Projection optical system and an exposure apparatus with the projection optical system

ABSTRACT

A projection optical system, which forms a reduced image of a first surface onto a second surface, has excellent optical performance without substantially being affected by birefringence despite the use of optical material having intrinsic birefringence. This is done by suitably arranging certain crystal axes of radiation transmissive members that make up the projection optical system relative to the optical axis of the projection optical system, and by suitably arranging the certain crystal axes of the radiation transmissive members relative to the crystal axes of other radiation transmissive members in the projection optical system.

This is a Division of application Ser. No. 10/183,612 filed Jun. 28,2002, which claims the benefit of U.S. Provisional Application No.60/308,867 filed Aug. 1, 2001. The entire disclosure of the priornon-provisional application is hereby incorporated by reference hereinin its entirety. The disclosure of Japanese Priority Application No.2001-196123 filed Jun. 28, 2001, is incorporated herein by reference inits entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a projection optical system and anexposure apparatus provided with a projection optical system. Inparticular, the present invention relates to a suitable catadioptrictype projection optical system in an exposure apparatus used whenfabricating microdevices such as semiconductors or the like in aphotolithographic process.

2. Description of Related Art

In recent years, the miniaturization in semiconductor device fabricationand semiconductor chip packaging fabrication is increasing, and aprojection optical system with a higher resolution is required for aphotolithographic exposure device. To satisfy this resolutionrequirement, the wavelength of the exposure light is shortened, and theNA (the numerical aperture of a projection optical system) is increased.However, when the wavelength of the exposure light is shortened, thetypes of optical glass that are able to be used are limited due to lightabsorption.

For example, when using light in a vacuum ultraviolet region with awavelength of 200 nm or less, an F₂ laser (wavelength 157 nm) inparticular, as the exposure light, a fluoride crystal such as calciumfluoride (fluorite: CaF₂) and barium fluoride (BaF₂) must be used as aradiation transmissive optical material in the projection opticalsystem. In reality, a design that forms a projection optical system withonly fluorite is assumed in an exposure apparatus using an F₂ laser.Fluorite is a cubic system that was thought to be optically isotropicand to have substantially no birefringence. Further, in prior visiblelight experiments, only low birefringence (random occurrences caused byinternal stress) has been observed in fluorite.

However, at a symposium (2nd International Symposium on 157 nmLithography) concerning lithography held on May 15, 2001, John H.Burnett et al. of the U.S. NIST announced that he confirmed both intheory and by experiment that fluorite has an intrinsic birefringence.

According to this presentation, fluorite birefringence is nearly zero inthe crystal axis direction [111] and the equivalent axes [-111], [1-11]and [11-1], and in the crystal axis [100] and equivalent axes [010] and[001], but other directions have a value which is not substantiallyzero. In particular, the six crystal axis directions [110], [-110],[101], [-101], [001] and [01-1] have a maximum birefringence of 6.5nm/cm for a wavelength of 157 nm and 3.6 nm/cm for a wavelength of 193nm. These values of birefringence are substantially greater than 1nm/cm, the permissible value of random birefringence. However, for theportion that is not random the effect of birefringence may accumulatethrough multiple lenses.

Previously, the birefringence of fluorite was not considered indesigning a projection optical system, so from the perspective ofworking ease, the crystal axis [111] and the optical axis are generallyaligned. In such a case, in a projection optical system, the NA(numerical aperture) is comparatively large, so the crystal performancemay deteriorate due to the effect of birefringence because the light raythat is somewhat tilted from the crystal axis [111] also passes throughthe lens.

However, Burnett et al. revealed in the presentation mentioned above, amethod of compensating for the effect of birefringence by aligning theoptical axis of a pair of fluorite lenses with the crystal axis [111]and rotating a pair of fluorite crystals 60° relatively with the opticalaxis at the center. It is possible to alleviate the effect ofbirefringence with this method, but the effect of the compensation isnot sufficient because the effect of birefringence is not activelycompensated for due to the effect of birefringence in the oppositedirection.

Also, when using F₂ laser light (157 nm wavelength) as an exposurelight, the outgas from the photoresist caused by exposure isunavoidable. Therefore, unless extraordinary steps are taken, it isimpossible to avoid a contamination of the lenses caused by outgas in aconventional projection optical system having a large numericalaperture.

SUMMARY OF THE INVENTION

The present invention addresses the above-described problems. One objectof the present invention is to provide a projection optical systemhaving excellent optical performance that is substantially not affectedby birefringence even when using optical materials with intrinsicbirefringence such as fluorite, for example, and to provide an exposureapparatus having the projection optical system. A further object of thepresent invention is to provide a projection optical system capable ofeffectively avoiding contamination of the lenses caused by outgas fromthe photoresist, and to provide an exposure apparatus as part of theprojection optical system.

In order to address the above-described problems, a first aspect of thepresent invention provides a projection optical system capable offorming a reduced image of a first surface onto a second surface, andincludes a plurality of lenses and at least one concave reflectivemirror, wherein the projection optical system, when used in an exposureapparatus to scan expose the first surface onto the second surface whilemoving the first surface and the second surface along a scanningdirection, forms a slit-shaped or arc-shaped exposure area at the secondsurface when not scanning; and satisfies the conditional expression0.5<(Dw·Nw)/Ew<1.4  (1)

-   -   where Dn is a working distance of the second surface side, Nw is        a numerical aperture of the second surface side, and Ew is a        length in the direction orthogonal to the scanning direction in        the slit-shaped or arc-shaped exposure area. It should be noted        that a slit shape in the present invention refers to a shape        extending in a direction across a scanning direction, for        example, a rectangular, trapezoidal or hexagonal shape extending        in a direction across a scanning direction.

According to a preferred embodiment of the first aspect of theinvention, a projection optical system has a slit-shaped or arc-shapedexposure area that does not intersect the optical axis of the projectionoptical system. The projection optical system is provided with arefractive type first optical imaging system to form a firstintermediate image of a first surface; a second optical imaging system,having at least one negative lens and a concave reflective mirror, toform the first intermediate image into a second intermediate image ofnearly the same magnification near the first intermediate image formingposition based on the light beam from the first intermediate image; arefractive type third optical imaging system to form a reduced image ofthe second intermediate image onto a second surface based on the lightbeam from the second intermediate image; a first optical path foldingmirror arranged in the optical path between the first optical imagingsystem and the second optical imaging system; and a second optical pathfolding mirror arranged in the optical path between the second opticalimaging system and the third optical imaging system. In this case, theeffective area of the first optical path folding mirror and theeffective area of the second optical path folding mirror preferably havea reflective surface formed across the whole of the planar surface. Itis preferable that the effective area of the first optical path foldingmirror and the effective area of the second optical path folding mirrornot have a spatial overlap, and be arranged such that the whole lightbeam from the first surface is guided to the second surface.

Further, according to a preferred embodiment of the first aspect of theinvention, all lenses comprising the first optical imaging system andthe third optical imaging system are arranged along a single straightline along the optical axis. Furthermore, in the first aspect of thepresent invention, the projection optical system is preferably providedwith a catadioptric type imaging system including a concave reflectivemirror arranged in the optical path between the first surface and thesecond surface; a refractive type imaging system arranged in the opticalpath between the catadioptric type optical imaging system and the secondsurface; a first optical path folding mirror arranged in the opticalpath between the first surface and the catadioptric type optical imagingsystem; and a second optical path folding mirror placed in the opticalpath arranged in the optical path between the catadioptric type opticalimaging system and the refractive type optical imaging system.

A second aspect of the present invention provides a projection opticalsystem including a plurality of lenses, a concave reflective mirror anda negative lens arranged in proximity to the concave reflective mirror,and is capable of forming a reduced image of a first surface at a secondsurface. The projection optical system, when used in an exposureapparatus to scan expose the first surface at the second surface whilemoving the first surface and the second surface along a scanningdirection, forms a slit-shaped or arc-shaped exposure area at the secondsurface when not scanning; and the numerical aperture of the secondsurface side is 0.82 or more.

In one example, the concave reflective mirror and the negative lens arearranged along an optical axis in a direction substantially differentfrom the direction of gravity, and the following conditional expressionis satisfied:1.0<S/|R|<1.8  (2)

-   -   wherein S is the clear aperture (diameter) of the concave        reflective mirror and R is the radius of curvature of the        concave reflective mirror. Further, in the second aspect of the        present invention, the projection optical system is preferably        provided with a catadioptric type imaging system including a        concave reflective mirror arranged in the optical path between        the first surface and the second surface; a refractive type        imaging system arranged in the optical path between the        catadioptric type optical imaging system and the second surface;        a first optical path folding mirror arranged in the optical path        between the first surface and the catadioptric type optical        imaging system; and a second optical path folding mirror placed        in the optical path arranged in the optical path between the        catadioptric type optical imaging system and the refractive type        optical imaging system.

A third aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein the projection optical system is arranged in an opticalpath between a pupil position of the second surface side and the secondsurface, has a substantially transmissive characteristic for light witha wavelength of 200 nm or less, and is provided with at least oneradiation transmissive member formed such that a crystal axis [100] oran optically equivalent crystal axis to the crystal axis [100] nearlyaligns with the optical axis.

A fourth aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein at least one radiation transmissive member of theradiation transmissive members exceeding a maximum angle of thetransmitting light ray of 20 degrees to the optical axis hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less, and is formed such that a crystal axis [100] or anoptically equivalent crystal axis to the crystal axis [100] nearlyaligns with the optical axis.

A fifth aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein the projection optical system is provided with: a firstgroup of transmissive members formed such that the crystal axis [100] oran optically equivalent crystal axis to the crystal axis [100] nearlyaligns with the optical axis, and has substantially transmissivecharacteristics for light with a wavelength of 200 nm or less; a secondgroup of transmissive members formed such that the crystal axis [100] oran optically equivalent crystal axis to the crystal axis [100] nearlyaligns with the optical axis, and has substantially transmissivecharacteristics for light with a wavelength of 200 nm or less; whereinthe first group of transmissive members and the second group oftransmissive members have a positional relationship relatively rotatedabout 45 degrees around the optical axis; and both the first group oftransmissive members and the second group of transmissive members arearranged in the optical path between the pupil position on the secondsurface side and the second surface.

A sixth aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein the projection optical system is provided with: a firstgroup of radiation transmissive members formed such that the crystalaxis [100] or an optically equivalent crystal axis to the crystal axis[100] nearly aligns with the optical axis, and has substantiallytransmissive characteristics for light with a wavelength of 200 nm orless; a second group of radiation transmissive members formed such thatthe crystal axis [100] or an optically equivalent crystal axis to thecrystal axis [100] nearly aligns with the optical axis, and hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; wherein the first group of radiation transmissivemembers and the second group of radiation transmissive members have apositional relationship relatively rotated about 45 degrees around theoptical axis; and in both the first group of radiation transmissivemembers and the second group of radiation transmissive members, themaximum angle of the transmitting light ray to the optical axis isgreater than 20 degrees.

It should be noted that in the fifth and sixth aspects of the presentinvention, to relatively rotate the first group of lens elements and thesecond group of lens elements about 45 degrees around the optical axismeans that the relative angle of the predetermined crystal axes (forexample, crystal axes [010], [001], [01-1], or [011]) which are facingin different directions from the optical axis in the first group of lenselements and the second group of lens elements is about 45 degreesaround the optical axis. Furthermore, when the crystal axis [100] servesas the optical axis, rotational asymmetry stemming from the effect ofbirefringence with the optical axis at the center appears at a 90 degreeperiod, so in the fifth and sixth aspects of the invention, torelatively rotate only about 45 degrees around the optical axis meansthe same as relatively rotating only about 45 degrees+(n*90 degrees)around the optical axis (where n is a whole number).

According to preferred embodiments of the fifth and sixth aspects of theinvention, at least one of the first group of radiation transmissivemembers and the second group of radiation transmissive members has atleast one aspherical surface. Further, it is preferable that theconditional expression |T1−T2|/TA<0.025 is satisfied, wherein T1 is thetotal thickness (center thickness) of the first group of radiationtransmissive members along the optical axis, T2 is the total thicknessof the second group of radiation transmissive members along the opticalaxis, and TA is the total thickness along the optical axis of all theradiation transmissive members comprising the projection optical system.Furthermore, the first group of radiation transmissive members and thesecond group of radiation transmissive members are preferably formed asone optical member by optical contact or by adhesion.

A seventh aspect of the present invention provides a projection opticalsystem which includes a plurality of lenses, a concave reflective mirrorand a negative lens arranged in proximity to the concave reflectivemirror, and which is capable of forming a reduced image of a firstsurface at a second surface, wherein the negative lens has substantiallytransmissive characteristics for light with a wavelength of 200 nm orless, and is formed such that the crystal axis [100] or an opticallyequivalent crystal axis to the crystal axis [100] nearly aligns with theoptical axis.

An eighth aspect of the present invention provides a projection opticalsystem including a plurality of lenses, a concave reflective mirror, anda first negative lens and a second negative lens arranged in proximityto the concave reflective mirror, and capable of forming a reduced imageof a first surface at a second surface, wherein: a) the first negativelens is formed such that the crystal axis [100] or an opticallyequivalent crystal axis to the crystal axis [100] nearly aligns with theoptical axis, and has substantially transmissive characteristics forlight with a wavelength of 200 nm or less; b) the second negative lensis formed such that the crystal axis [100] or an optically equivalentcrystal axis to the crystal axis [100] nearly aligns with the opticalaxis, and has substantially transmissive characteristics for light witha wavelength of 200 nm or less; and c) the first negative lens andsecond negative lens have a positional relationship relatively rotatedonly about 45 degrees around the optical axis.

It should be noted that in the eighth aspect of the present invention,to relatively rotate a first negative lens and a second negative lensabout 45 degrees around the optical axis means that the relative angleof the predetermined crystal axes (for example, crystal axes [010],[001], [01-1], or [011]) which are facing in different directions fromthe optical axis in a first negative lens and a second negative lens isabout 45 degrees around the optical axis. Furthermore, when the crystalaxis [100] serves as the optical axis, rotational asymmetry stemmingfrom the effect of birefringence with the optical axis at the centerappears at a 90 degree period, so in the eighth aspect of the invention,to relatively rotate only about 45 degrees around the optical axis meansthe same as relatively rotating only about 45 degrees+(n*90 degrees)around the optical axis (where n is a whole number).

A ninth aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein the projection optical system is arranged in theoptical path between the pupil position of the second surface side andthe second surface, has a substantially transmissive characteristic forlight with a wavelength of 200 nm or less, and is provided with at leastone radiation transmissive member formed such that the crystal axis[110] or an optically equivalent crystal axis to the crystal axis [110]nearly aligns with the optical axis.

A tenth aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein at least one radiation transmissive member of theradiation transmissive members exceeding a maximum angle of thetransmitting light ray of 20 degrees to the optical axis hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less, and is formed such that the crystal axis [110] or anoptically equivalent crystal axis to the crystal axis [110] nearlyaligns with the optical axis.

An eleventh aspect of the present invention provides a projectionoptical system capable of forming a reduced image of a first surface ata second surface, wherein the projection optical system is providedwith: a third group of transmissive members formed such that the crystalaxis [100] or an optically equivalent crystal axis to the crystal axis[100] nearly aligns with the optical axis, and has substantiallytransmissive characteristics for light with a wavelength of 200 nm orless; a fourth group of transmissive members formed such that thecrystal axis [100] or an optically equivalent crystal axis to thecrystal axis [100] nearly aligns with the optical axis, and hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; wherein the third group of transmissive members andthe fourth group of transmissive members have a positional relationshiprelatively rotated about 90 degrees around the optical axis; and boththe third group of transmissive members and the fourth group oftransmissive members are arranged in the optical path between the pupilposition on the second surface side and the second surface.

A twelfth aspect of the present invention provides a projection opticalsystem capable of forming a reduced image of a first surface at a secondsurface, wherein the projection optical system is provided with: a thirdgroup of radiation transmissive members formed such that the crystalaxis [110] or an optically equivalent crystal axis to the crystal axis[110] nearly aligns with the optical axis, and has substantiallytransmissive characteristics for light with a wavelength of 200 nm orless; a fourth group of radiation transmissive members formed such thatthe crystal axis [110] or an optically equivalent crystal axis to thecrystal axis [110] nearly aligns with the optical axis, and hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; wherein the third group of radiation transmissivemembers and the fourth group of radiation transmissive members have apositional relationship relatively rotated about 90 degrees around theoptical axis; and in both the third group of radiation transmissivemembers and the fourth group of radiation transmissive members, themaximum angle of the transmitting light ray to the optical axis isgreater than 20 degrees.

It should be noted that in the eleventh and twelfth aspects of thepresent invention, to relatively rotate the first group of lens elementsand the second group of lens elements about 90 degrees around theoptical axis means that the relative angle of the predetermined crystalaxes (for example, crystal axes [001], [-111], [-110], or [1-11]) whichare facing in different directions from the optical axis in the firstgroup of lens elements and the second group of lens elements is about 90degrees around the optical axis. Furthermore, when the crystal axis[110] serves as the optical axis, rotational asymmetry stemming from theeffect of birefringence with the optical axis at the center appears at a180 degree period, so in the eleventh and twelfth aspects of theinvention, to relatively rotate only about 90 degrees around the opticalaxis means the same as relatively rotating only about 90 degrees+(n*180degrees) around the optical axis (where n is a whole number).

According to preferred embodiments in the eleventh and twelfth aspectsof the invention, at least one of the third group of radiationtransmissive members and the fourth group of radiation transmissivemembers has at least one aspherical surface. Further, it is preferablethat the conditional expression |T3−T4|/TA<0.025 is satisfied, whereinT3 is the total thickness (center thickness) of the third group ofradiation transmissive members along the optical axis, T4 is the totalthickness of the fourth group of radiation transmissive members alongthe optical axis, and TA is the total thickness along the optical axisof all the radiation transmissive members comprising the projectionoptical system. Furthermore, the third group of radiation transmissivemembers and the fourth group of radiation transmissive members arepreferably formed as one optical member by optical contact or byadhesion.

A thirteenth aspect of the present invention provides a projectionoptical system which includes a plurality of lenses, a concavereflective mirror and a negative lens arranged in proximity to theconcave reflective mirror, and which is capable of forming a reducedimage of a first surface at a second surface, wherein the negative lenshas substantially transmissive characteristics for light with awavelength of 200 nm or less, and is formed such that the crystal axis[110] or an optically equivalent crystal axis to the crystal axis [110]nearly aligns with the optical axis.

A fourteenth aspect of the present invention provides a projectionoptical system including a plurality of lenses, a concave reflectivemirror, and a first negative lens and a second negative lens arranged inproximity to the concave reflective mirror, and capable of forming areduced image of a first surface at a second surface, wherein: the firstnegative lens is formed such that the crystal axis [110] or an opticallyequivalent crystal axis to the crystal axis [110] nearly aligns with theoptical axis, and has substantially transmissive characteristics forlight with a wavelength of 200 nm or less; the second negative lens isformed such that the crystal axis [110] or an optically equivalentcrystal axis to the crystal axis [110] nearly aligns with the opticalaxis, and has substantially transmissive characteristics for light witha wavelength of 200 nm or less; and the first negative lens and secondnegative lens have a positional relationship relatively rotated about 90degrees around the optical axis.

It should be noted that in the fourteenth aspect of the presentinvention, to relatively rotate the first negative lens and the secondnegative lens about 90 degrees around the optical axis means that therelative angle of the predetermined crystal axes (for example, crystalaxes [001], [-111], [-110], or [1-11]) which are facing in differentdirections from the optical axis in the first group of lens elements andthe second group of lens elements is about 90 degrees around the opticalaxis. Furthermore, when the crystal axis [110] serves as the opticalaxis, rotational asymmetry stemming from the effect of birefringencewith the optical axis at the center appears at a 180 degree period, soin the fourteenth aspect of the invention, to relatively rotate onlyabout 90 degrees around the optical axis means the same as relativelyrotating only about 90 degrees+(n*180 degrees) around the optical axis(where n is a whole number).

A fifteenth aspect of the present invention provides a projectionoptical system capable of forming a reduced image of a first surface ata second surface, wherein the projection optical system is providedwith: a fifth group of radiation transmissive members formed such thatthe crystal axis [111] or an optically equivalent crystal axis to thecrystal axis [111] nearly aligns with the optical axis, and hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; a sixth group of radiation transmissive membersformed such that the crystal axis [111] or an optically equivalentcrystal axis to the crystal axis [111] nearly aligns with the opticalaxis, and has substantially transmissive characteristics for light witha wavelength of 200 nm or less; wherein the fifth group of radiationtransmissive members and the sixth group of radiation transmissivemembers have a positional relationship relatively rotated about 60degrees around the optical axis; and both the fifth group of radiationtransmissive members and the sixth group of radiation transmissivemembers are arranged in the optical path between the pupil position onthe second surface side and the second surface.

A sixteenth aspect of the present invention provides a projectionoptical system capable of forming a reduced image of a first surface ata second surface, wherein the projection optical system is providedwith: a fifth group of radiation transmissive members formed such thatthe crystal axis [111] or an optically equivalent crystal axis to thecrystal axis [111] nearly aligns with the optical axis, and hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; a sixth group of radiation transmissive membersformed such that the crystal axis [111] or an optically equivalentcrystal axis to the crystal axis [111] nearly aligns with the opticalaxis, and has substantially transmissive characteristics for light witha wavelength of 200 nm or less; wherein the fifth group of radiationtransmissive members and the sixth group of radiation transmissivemembers have a positional relationship relatively rotated about 60degrees around the optical axis; and in both the fifth group ofradiation transmissive members and the sixth group of radiationtransmissive members, the maximum angle of the transmitting light ray tothe optical axis is greater than 20 degrees.

It should be noted that in the eleventh and twelfth aspects of thepresent invention, to relatively rotate the fifth group of radiationtransmissive members and the sixth group of radiation transmissivemembers about 60 degrees around the optical axis means that the relativeangle of the predetermined crystal axes (for example, crystal axes[-111], [11-1], or [1-11]) which are facing in different directions fromthe optical axis in the fifth group of radiation transmissive membersand the sixth group of radiation transmissive members is about 60degrees around the optical axis. Furthermore, when the crystal axis[111] serves as the optical axis, rotational asymmetry stemming from theeffect of birefringence with the optical axis at the center appears at a120 degree period, so in the eleventh and twelfth aspects of theinvention, to relatively rotate only about 60 degrees around the opticalaxis means the same as relatively rotating only about 60 degrees+(n*120degrees) around the optical axis (where n is a whole number).

According to preferred embodiments of the fifteenth and sixteenthaspects of the invention, at least one of the fifth group of radiationtransmissive members and the sixth group of radiation transmissivemembers has at least one aspherical surface. Further, it is preferablethat the conditional expression |T5−T6|/TA<0.025 is satisfied, whereinT5 is the total thickness (center thickness) of the fifth group ofradiation transmissive members along the optical axis, T6 is the totalthickness of the sixth group of radiation transmissive members along theoptical axis, and TA is the total thickness along the optical axis ofall the radiation transmissive members comprising the projection opticalsystem. Furthermore, the fifth group of radiation transmissive membersand the sixth group of radiation transmissive members are preferablyformed as one optical member by optical contact or by adhesion.

A seventeenth aspect of the present invention provides a projectionoptical system including a plurality of lenses, a concave reflectivemirror, and a first negative lens and a second negative lens arranged inproximity to the concave reflective mirror, and capable of forming areduced image of a first surface at a second surface, wherein: the firstnegative lens is formed such that the crystal axis [111] or an opticallyequivalent crystal axis to the crystal axis [111] nearly aligns with theoptical axis, and has substantially transmissive characteristics forlight with a wavelength of 200 nm or less; the second negative lens isformed such that the crystal axis [111] or an optically equivalentcrystal axis to the crystal axis [111] nearly aligns with the opticalaxis, and has substantially transmissive characteristics for light witha wavelength of 200 nm or less; and the first negative lens and secondnegative lens have a positional relationship relatively rotated about 60degrees around the optical axis.

It should be noted that in the seventeenth aspect of the presentinvention, to relatively rotate the first negative lens and the secondnegative lens about 60 degrees around the optical axis means that therelative angle of the predetermined crystal axes (for example, crystalaxes [-111], [11-1], or [1-11]) which are facing in different directionsfrom the optical axis in the first group of lens elements and the secondgroup of lens elements is about 60 degrees around the optical axis.Furthermore, when the crystal axis [111] serves as the optical axis,rotational asymmetry stemming from the effect of birefringence with theoptical axis at the center appears at a 120 degree period, so in theseventeenth aspect of the invention, to relatively rotate only about 60degrees around the optical axis means the same as relatively rotatingonly about 60 degrees+(n*120 degrees) around the optical axis (where nis a whole number).

An eighteenth aspect of the present invention provides a projectionoptical system capable of forming a reduced image of a first surface ata second surface, wherein the projection optical system: is providedwith a radiation transmissive member formed of a crystal havingsubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; and a crystal coat formed on the crystal is formed onthe surface of the radiation transmissive member; and the crystaldirection of the radiation transmissive member and the crystal directionof the crystal coat are different.

According to a preferred embodiment of the eighteenth aspect of theinvention, the crystal direction along the optical axis of the radiationtransmissive member and the crystal direction along the optical axis ofthe crystal coat are different. Alternatively, the crystal directionalong the optical axis of the radiation transmissive member and thecrystal direction along the optical axis of the crystal coat nearly thesame, and the radiation transmissive member and the crystal coatpreferably have a positional relationship relatively rotated apredetermined angle around the optical axis.

Here, a radiation transmissive member and a crystal coat having apositional relationship relatively rotated a predetermined angle aroundthe optical axis means that the relative angle around the optical axisof specified crystal axes facing different directions from the opticalaxis in a radiation transmissive member and a crystal coat is apredetermined angle.

A nineteenth aspect of the present invention provides a projectionoptical system capable of forming a reduced image of a first surface ata second surface, wherein the projection optical system is providedwith: a first group of radiation transmissive members formed such thatthe crystal axis [100] or an optically equivalent crystal axis to thecrystal axis [100] nearly aligns with the optical axis, and hassubstantially transmissive characteristics for light with a wavelengthof 200 nm or less; a third group of radiation transmissive membersformed such that the crystal axis [110] or an optically equivalentcrystal axis to the crystal axis [110] nearly aligns with the opticalaxis, and has substantially transmissive characteristics for light witha wavelength of 200 nm or less; and a fifth group of radiationtransmissive members formed such that the crystal axis [111] or anoptically equivalent crystal axis to the crystal axis [111] nearlyaligns with the optical axis, and has substantially transmissivecharacteristics for light with a wavelength of 200 nm or less.

According to preferred embodiments of the invention, the projectionoptical system is used in an exposure apparatus that moves the firstsurface and the second surface along a scan direction to scan expose animage of the first surface onto the second surface, and a slit-shaped orarc-shaped exposure area does not intersect the optical axis of theprojection optical system. The projection optical system preferably isprovided with: a refractive type first optical imaging system to form afirst intermediate image of the first surface; a second optical imagingsystem, having at least one negative lens and a concave reflectivemirror, to form the first intermediate image into a second intermediateimage of nearly the same magnification near the first intermediate imageforming position, based on the light beam from the first intermediateimage; a refractive type third optical imaging system to form a reducedimage of the second intermediate image onto the second surface based onthe light beam from the second intermediate image; a first optical pathfolding mirror arranged in the optical path between the first opticalimaging system and the second optical imaging system; and a secondoptical path folding mirror arranged in the optical path between thesecond optical imaging system and the third optical imaging system.

It should be noted that in the above-described embodiments, theeffective area of the first optical path folding mirror and theeffective area of the second optical path folding mirror preferably havea reflective surface formed across the whole of the planar surface. Itis preferable that the effective area of the first optical path foldingmirror and the effective area of the second optical path folding mirrordo not have a spatial overlap, and they are arranged such that the wholelight beam from the first surface is guided to the second surface.Further, according to the above-described embodiments, all lensescomprising the first optical imaging system and the third opticalimaging system are arranged along a single straight line of the opticalaxis. Furthermore, the projection optical system is preferably providedwith a catadioptric type imaging system including a concave reflectivemirror arranged in the optical path between the first surface and thesecond surface; a refractive type imaging system arranged in the opticalpath between the catadioptric type optical imaging system and the secondsurface; a first optical path folding mirror arranged in the opticalpath between the first surface and the catadioptric type optical imagingsystem; and a second optical path folding mirror placed in the opticalpath arranged in the optical path between the catadioptric type opticalimaging system and the refractive type optical imaging system.

Another aspect of the present invention provides an exposure apparatusprovided with: an illumination system to illuminate a mask serving asthe first surface, and a projection optical system according to any ofthe above aspects to form a pattern image formed on the mask at aphotosensitive substrate serving as the second surface.

Another aspect of the present invention provides an exposure method toilluminate a mask formed with a pattern, and to form an image of apattern of the mask onto a photosensitive substrate via a projectionoptical system according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIG. 1 is a diagram of the crystal axis directions of fluorite;

FIG. 2 is a diagram of the method of Burnett et al. and shows thebirefringence distribution for light ray incidence angles;

FIG. 3 is a diagram of a first method of the present invention, andshows the birefringence distribution for light ray incidence angles;

FIG. 4 is a diagram of a third method of the present invention, andshows the birefringence distribution for light ray incidence angles;

FIG. 5 is a schematic diagram of an exposure apparatus provided with anoptical system in the various embodiments of the present invention;

FIG. 6 is a diagram of the positional relationship between the opticalaxis and the rectangular-shaped exposure area (in other words, theeffective exposure area) formed on a wafer;

FIG. 7 is a diagram of the lens structure of the projection opticalsystem PL in the first example;

FIG. 8 is a diagram of the lateral distortion in the first example;

FIG. 9 is a diagram of the lens structure of the projection opticalsystem PL in the second example;

FIG. 10 is a diagram of the lateral distortion in the second example;

FIG. 11 is a flowchart of a method used to obtain a semiconductor deviceas one type of microdevice;

FIG. 12 is a flowchart of a method used to obtain a liquid crystaldisplay device as one type of microdevice;

FIG. 13 is a diagram showing a lens structure of a projection opticalsystem PL according to a third embodiment;

FIG. 14 is a diagram showing a rectangular-shaped exposure region (thatis, effective exposure region) formed on a wafer by a projection opticalsystem PL according to the third embodiment;

FIG. 15 is a diagram showing incident angle dependence of transmittanceof a thin film RE according to the third embodiment;

FIG. 16 is a diagram showing incident angle dependence of a phasedifference (polarization aberration) of a thin film RE according to thethird embodiment; and

FIG. 17 is a diagram showing a wavefront aberration of a projectionoptical system according to the third embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First, basic methods of the present invention for substantially avoidingthe affect of birefringence are described hereinafter. FIG. 1 shows thecrystal axis directions of fluorite. The crystal directions are definedbased on the XYZ coordinate system of a cubic crystal system. In otherwords, the crystal axis [100] is defined as the +X axis, the crystalaxis [010] is defined as the +Y axis and the crystal axis [001] isdefined as the +Z axis.

The crystal axis [101] on the XZ plane is defined as the direction 45degrees between the crystal axis [100] and the crystal axis [001]. Thecrystal axis [110] on the XY plane is defined as the direction 45degrees between the crystal axis [100] and the crystal axis.

The crystal axis [011] on the YZ plane is defined as the direction 45degrees between the crystal axis [001] and the crystal axis [010].

It should be noted that FIG. 1 shows only the crystal axes in the spacedefined by the +X axis, the +Y axis and the +Z axis, but crystal axesare defined similarly in other spaces. As described above, birefringenceis nearly zero (minimal) for fluorite in the crystal axis direction[111], shown as a solid line in FIG. 1, and the equivalent crystal axisdirections [-111], [1-11], [11-1] not depicted.

Similarly, birefringence is nearly zero (minimal) in the crystal axisdirections [100], [010], [011] shown as bold solid lines in FIG. 1. Onthe other hand, birefringence is maximum in the crystal axis directions[110], [101], [011] shown as bold dashed lines in FIG. 1, and theequivalent crystal axis directions [-110], [-101], [01-1] not depicted.

Prior to describing a method of the present invention below, thecorrection effectiveness for the above-described Burnett et al. methodwill be verified. FIG. 2 (FIGS. 2(a)-2(c)) shows the Burnett et. al.method and the distribution of the indices of double refraction(birefringence) for light ray incident angles. In FIG. 2, each of thefive concentric circles shown as dashed lines represent 10 degrees.Therefore, the innermost circle represents a 10 degree incidence anglerelative to the optical axis, and the outermost circle represents a 50degree incidence angle.

Moreover, a black circle represents an area with no birefringence havinga comparatively high refractive index, a white circle represents an areawith no birefringence having a comparatively low refractive index, thesmall hatched circle (see FIG. 4(c)) represents an area with nobirefringence having an intermediate refractive index. On the otherhand, the thick circle and the long double arrows represent thedirection of a comparatively high refractive index in the area withbirefringence, and the thin circle and short double arrows represent thedirection of a comparatively low refractive index in the area withbirefringence. The above-described notation is the same for FIGS. 3 and4.

As described above, the Burnett et al. method aligns the optical axes ofa pair of fluorite lenses with the crystal axis [111] and rotates thepair of fluorite lenses relatively 60 degrees around the optical axis.Thus, the distribution of the indices of double refraction in onefluorite lens is shown FIG. 2(a), and the distribution of the indices ofdouble refraction in the other fluorite lens is shown in FIG. 2(b). As aresult, the distribution of the indices of double refraction in the pairof fluorite lenses overall are shown in FIG. 2(c).

In this case, with reference to FIGS. 2(a) and (b), the areacorresponding to the crystal axis [111] which is aligned with theoptical axis is an area with no birefringence having a comparatively lowrefractive index. Further, the areas corresponding to the crystal axes[100], [010], [001] are areas with no birefringence having acomparatively high refractive index. Furthermore, the areascorresponding to the crystal axes [110], [101], [011] are areas ofbirefringence where the refractive index of the tangential polarizationis comparatively low and the refractive index of the radial polarizationis comparatively high. Thus, it is clear that the maximum effect ofbirefringence occurs in the area 35.26 degrees from the optical axis(the angle defined by the crystal axis [111] and the crystal axis [110])in each lens.

On the other hand, with reference to FIG. 2(c), the effect of thecrystal axes [110], [101], [011], where birefringence is maximum, can beameliorated for the pair of fluorite lenses overall by rotating the pairof fluorite lenses relatively 60 degrees. However, in the area 35.26degrees from the optical axis, in other words, the area comparativelynear the optical axis, an area of birefringence remains where therefractive index of tangential polarization is lower than the refractiveindex of radial polarization. As a result, a certain amount of theeffect of birefringence exists with the Burnett et al. method.

A first method of the present invention aligns the optical axis of afirst group of lens elements (radiation transmissive members) with theoptical axis [100] (or an optically equivalent crystal axis), theoptical axis of a second group of lens elements with the optical axis[100] (or an optically equivalent crystal axis), and relatively rotatesthe first group of lens elements and the second group of lens elementsonly 45 degrees around the optical axis. Here, the optically equivalentcrystal axes to the crystal axis [100] are crystal axes [010], [001].

FIG. 3 shows the first method of the present invention, and thedistribution of the indices of double refraction for the angle ofincidence of the light ray (the angle between the light ray and theoptical axis). In the first method, the distribution of the indices ofdouble refraction in the first group of lens elements is shown in FIG.3(a), and the distribution of the indices of double refraction in thesecond group of lens element is shown in FIG. 3(b). As a result, thedistribution of the indices of double refraction for the first group oflens elements and the second group of lens elements overall is shown inFIG. 3(c).

Referring to FIGS. 3(a) and 3(b), in the first method, the areacorresponding to the crystal axis [100] which is aligned with theoptical axis is an area with no birefringence having a comparativelyhigh refractive index. Further, the areas corresponding to the crystalaxes [111], [1-11], [-11-1], [11-1] are areas with no birefringencehaving a comparatively low refractive index. Further, the areascorresponding to crystal axes [101], [10-1], [110], [1-10] are areas ofbirefringence where the refractive index of the tangential polarizationis comparatively high and the refractive index of the radialpolarization is comparatively low. Thus, each group of lens elementsreceives the maximum effect of the indices of double refraction in thearea 45 degrees from the optical axis (the angle defined by the crystalaxis [100] and the crystal axis [101]).

On the other hand, with reference to FIG. 3(c), by relatively rotatingthe first group of lens elements and the second group of lens elements45 degrees around the optical axis, for the first group of lenses andthe second group of lenses overall, the effect of crystal axes [101],[10-1], [1 10], [1-10] where birefringence is maximum, can be fairlywell ameliorated, and in the area 45 degrees from the optical axis, inother words, the area separated from the optical axis, an area ofbirefringence remains where the refractive index of tangentialpolarization is higher than the refractive index of radial polarization.In this case, the maximum angle of the light beam and the optical pathfor each lens element in a common projection optical system is about 35to 40 degrees. Therefore, by adopting the first method, it possible toobtain excellent imaging performance without substantially receiving theeffect of the birefringence of crystal axes [101], [10-1], [1 10],[1-10].

It should be noted that in the first method of the present invention, torelatively rotate the first group of lens elements and the second groupof lens elements about 45 degrees around the optical axis means that therelative angle of the predetermined crystal axes (for example, crystalaxes [010], [001], [011] or [01-1]), which are facing in differentdirections from the optical axis in the first group of lens elements andin the second group of lens elements, is about 45 degrees around theoptical axis. For example, the relative angle of the crystal axis [010]in the first group of lens elements and of the crystal axis [010] in thesecond group of lens elements is 45 degrees around the optical axis.

Furthermore, as is clear from FIGS. 3(a) and 3(b), when the crystal axis[100] serves as the optical axis, rotational asymmetry stemming from theeffect of birefringence around the optical axis appears at a 90 degreeperiod. Therefore, in the first method, to relatively rotate only about45 degrees around the optical axis means the same as relatively rotatingonly about 45 degrees+(n*90 degrees) around the optical axis, that is,45 degrees, 135 degrees, 225 degrees or 315 degrees (where n is a wholenumber).

It should be noted that in the description above, the first group oflens elements and the second group of lens elements each have one or aplurality of lenses. When the first group of lens elements or the secondgroup of lens elements include a plurality of lenses, the plurality oflenses are not necessarily continuous lenses. The concept of groups oflens elements applies to the third through the sixth group of lenselements as well. In the first method, the total T1 of the thickness ofthe first group of lens elements along the optical axis and the total T2of the thickness of the second group of lens elements along the opticalaxis are preferably nearly equal.

Also, with reference to FIGS. 2(a) and (b), because the optical axis ofthe lens elements and the crystal axis [111] are aligned, the areascorresponding to the crystal axes [110], [101], [011] wherebirefringence is maximum exist at a 120 degree pitch, and it is possiblethat the effect of birefringence, that is, coma aberrations in the imagesurface (the wafer surface), having a 3 θ distribution surface may begenerated within the pupil. In contrast, with reference to FIGS. 3(a)and (b), because the optical axis of the lens elements and the crystalaxis [100] are aligned, the areas corresponding to the crystal axes[101], [10-1], [110], [1-10] where birefringence is maximum exist at a90 degree pitch, and the effect of birefringence having a 4 θdistribution may appear within the pupil plane.

In this case, because the vertical and horizontal patterns in thepattern to be projected onto the wafer are dominant, if the distributionis 4 θ, astigmatism of the vertical and horizontal patterns is notgenerated and image degradation is not large. Therefore, by adopting thesecond method to align the optical axis of at least one lens elementwith the crystal axis [100] (or an optically equivalent crystal axis),it possible to effectively suppress the effect of birefringence and toobtain excellent imaging performance.

Further, in the third method of the present invention, the optical axisof the third group of lens elements is aligned with the crystal axis[110] (or an optically equivalent crystal axis), the fourth group oflens elements is aligned with the crystal axis [110] (or an opticallyequivalent crystal axis), and the third group of lens elements and thefourth group of lens elements are relatively rotated only 90 degreesaround the optical axis. Here, the optically equivalent crystal axes tothe crystal axis [110] are the crystal axes [-110], [101], [-101], [011]and [01-1].

FIG. 4 shows a third method of the present invention, and thedistribution of the indices of double refraction for the angle ofincidence of the light ray. In the third method, the distribution of theindices of double refraction in the third group of lens elements isshown in FIG. 4(a), and the distribution of the indices of doublerefraction in the fourth group of lens elements is shown in FIG. 4(b).As a result, the distribution of the indices of double refraction forthe third group of lens elements and the fourth group of lens elementsoverall is shown in FIG. 4(c).

Referring to FIGS. 4(a) and 4(b), in the third method, the areacorresponding to the crystal axis [110] which is aligned with theoptical axis is a birefringent area with comparatively high refractiveindex to one direction of polarization and a comparatively lowrefractive index to the other (the direction orthogonal to the directionof the first) direction of polarization. Further, the areascorresponding to the crystal axes [100] and [010] are areas with nobirefringence having a comparatively high refractive index. Furthermore,the areas corresponding to crystal axes [111] and [11-1] are areas withno birefringence having a comparatively low refractive index.

On the other hand, with reference to FIG. 4(c), by relatively rotatingthe third group of lens elements and the fourth group of lens elements90 degrees around the optical axis, for the third group of lens elementsand the fourth group of lens elements overall, the effect of crystalaxis [110] where birefringence is maximum is almost nonexistent, and thearea near the optical axis is an area with no birefringence having anintermediate refractive index. In other words, by adopting the thirdmethod it is possible to obtain excellent imaging performance withoutsubstantially receiving the effect of birefringence.

It should be noted that in the third method of the present invention, torelatively rotate the third group of lens elements and the fourth groupof lens elements about 90 degrees around the optical axis means that therelative angle of the predetermined crystal axes (for example, crystalaxes [001], [-111], [-110], or [1-11]) which are facing in differentdirections from the optical axis in the third group of lens elements andthe fourth group of lens elements is about 90 degrees around the opticalaxis. For example, the relative angle of the crystal axis [001] in thethird group of lens elements and the crystal axis [001] in the fourthgroup of lens elements is 90 degrees around the optical axis.

Furthermore, as is clear in FIGS. 4(a) and 4(b), when the crystal axis[110] serves as the optical axis, rotational asymmetry stemming from theeffect of birefringence around the optical axis appears at a 180 degreeperiod. Therefore, in the third method, to relatively rotate only about90 degrees around the optical axis means the same as relatively rotatingonly about 90 degrees+(n*180 degrees) around the optical axis, that is,90 degrees, 270 degrees, and so forth (where n is a whole number).

In the third method also, the total T3 of the thickness of the thirdgroup of lens elements along the optical axis and the total T4 of thethickness of the fourth group of lens elements along the optical axisare preferably nearly equal. In particular, in the third method, becausethe birefringent area (the optical axis and its proximal area) is in thecenter portion, it is preferable that a negative lens with a thin centerportion be chosen.

Further, due to the same reason as that described in the above-describedsecond method, by adopting a fourth method which aligns the optical axisof at least one lens element and the crystal axis [110] (or an opticallyequivalent crystal axis), it possible to effectively suppress the effectof birefringence and to obtain excellent imaging performance.

Moreover, the above-described Burnett et al. method is used as part of afifth method of the present invention. In this case, the fifth method ofthe present invention aligns the optical axis of the fifth group of lenselements and the crystal axis [111] (or an optically equivalent crystalaxis), aligns the optical axis of the sixth group of lens elements andthe crystal axis [111] (or an optically equivalent crystal axis), andrelatively rotates the fifth group of lens elements and the sixth groupof lens elements only 60 degrees around the optical axis.

As described above, by adopting the fifth method, it is possible toeffectively suppress the effect of birefringence and to obtain excellentimaging performance. Here, an optically equivalent crystal axes tocrystal axis [111] are crystal axes [-111], [1-11], [11-1].

It should be noted that in the fifth method of the present invention, torelatively rotate the fifth group of lens elements and the sixth groupof lens elements about 60 degrees around the optical axis means that therelative angle of the predetermined crystal axes (for example, crystalaxes [-111], [11-1], or [1-11]) which are facing in different directionsfrom the optical axis in the fifth group of lens elements and the sixthgroup of lens elements is about 60 degrees around the optical axis. Forexample, the relative angle of the crystal axis [-111] in the fifthgroup of lens elements and the crystal axis [-111] in the sixth group oflens elements is 60 degrees around the optical axis.

Furthermore, as is clear from FIGS. 2(a) and 2(b), when the crystal axis[111] serves as the optical axis, rotational asymmetry stemming from theeffect of birefringence around the optical axis appears at a 120 degreeperiod. Therefore, in the fifth method, to relatively rotate only about60 degrees around the optical axis means the same as relatively rotatingonly about 60 degrees+(n*120 degrees) around the optical axis, that is,60 degrees, 180 degrees, 300 degrees, and so forth (where n is a wholenumber).

In the fifth method, the total T5 of the thickness of the fifth group oflens elements along the optical axis and the total T6 of the thicknessof the sixth group of lens elements along the optical axis arepreferably nearly equal.

Moreover, as a sixth method of the present invention, it is possible toadopt a method combining portions of methods 1, 3 and 5. In other words,the sixth method of the present invention aligns the optical axis of thefirst group of lens elements and the crystal axis [100 ](or an opticallyequivalent crystal axis), aligns the optical axis of the third group oflens elements and the crystal axis [110] (or an optically equivalentcrystal axis), and aligns the optical axis of the fifth group of lenselements and the crystal axis [111] (or an optically equivalent crystalaxis). In this case, it is possible to effectively suppress the effectof birefringence and to obtain excellent imaging performance.

In the present invention, as described below, one of the above-describedsix methods has been selected and applied to predetermined opticalmembers of the projection optical system. Additionally, in the presentinvention, it is possible to adopt a combination of a plurality ofmethods selected from the above-described six methods. Thus, in thepresent invention, even though birefringent optical materials such asfluorite are used in the projection optical system, it is possible torealize a projection optical system having excellent imaging performancewithout substantially receiving the effect of birefringence.

It should be noted that in a lens with the crystal axis [111] set in theoptical axis direction, polishing errors on the lens surface are easilymanifest at every 120 degrees azimuth angle around the optical axis dueto the crystal structure. Nevertheless, as in the above-mentioned fifthmethod, this method has the advantage of making it possible to nearlyoffset aberrations between the fifth group of lens elements and thesixth group of lens elements resulting from polishing errors on the lenssurface at every 120 degrees azimuth angle around the optical axis byaligning the optical axis of the fifth group of lens elements and thecrystal axis [I 11] (or an optically equivalent crystal axis), aligningthe optical axis of the sixth group of lens elements and the crystalaxis [111] (or an optically equivalent crystal axis), and relativelyrotating the fifth group of lens elements and the sixth group of lenselements only 60 degrees around the optical axis.

However, in the present invention, the following conditional expressions(3) through (5) are preferably satisfied in the above-described firstmethod, third method and fifth method.|T1−T2|/TA<0.025  (3)|T3−T4|/TA<0.025  (4)|T5−T6|/TA<0.025  (5)

Here, T1 through T6, as described above, are the totals of the thicknessalong the optical axis of the first through sixth groups of lenses(radiation transmissive members). Moreover, TA is the total thicknessalong the optical axis of all the radiation transmissive memberscomprising the projection optical system. It is not preferable thatexpressions (3) through (5) are not satisfied because the effect ofbirefringence becomes high and the imaging performance of the opticalsystem worsens.

Next, according to a different aspect of the present invention, in acatadioptric projection optical system which forms a reduced image of afirst surface onto a second surface and includes a plurality of lensesand at least one concave reflective mirror, contamination of the lensescaused by outgas from the photoresist is effectively avoided. For thispurpose, the present invention, when used in an exposure apparatus toscan expose the first surface onto the second surface while moving thefirst surface and the second surface along a scanning direction, forms aslit-shaped or arc-shaped exposure area at the second surface when notscanning; and satisfies the following conditional expression (1).0.5<(Dw·Nw)/Ew<1.4  (1)

Here, Dw is the working distance (the distance between the secondsurface and the most second surface side of the closest optical member)of the second surface, Nw is the numerical aperture (the image sidenumerical aperture) of the second surface and Ew is the length along thenon-scanning direction (the direction orthogonal to the scanningdirection) in the slit-shaped or arc-shaped exposure area. Theconditional expression (1) determines the relationship between the imageside working distance, the image side numerical aperture and the imagefield. If the conditional expression (1) is below the lower limit, thencontamination caused by outgas from the photoresist coated on thesurface of the photosensitive substrate is greater. On the other hand,if the conditional expression (1) is above the upper limit, then notonly does it become difficult to correct chromatic aberration, but it isimpossible to avoid increasing the size of the optical elements, andoptical system manufacture becomes difficult. It should be noted that tofurther demonstrate the excellent effect of the present invention, thelower limit of the conditional expression is preferably 0.53 and theupper limit is 1.3.

Also, in the above-described catadioptric projection optical system, theslit-shaped or arc-shaped exposure area is set such that the opticalaxis of the projection optical system is not included (i.e., the opticalaxis does not pass through the exposure area), and the above-describedcatadioptric projection optical system is provided with a refractivetype first optical imaging system to form a first intermediate image ofthe first surface; a second optical imaging system, having at least onenegative lens and a concave reflective mirror, to form the firstintermediate image into a second intermediate image of nearly the samemagnification near the first intermediate image forming position, basedon the light beam from the first intermediate image; a refractive typethird optical imaging system to form a reduced image of the secondintermediate image onto the second surface based on the light beam fromthe second intermediate image; a first optical path folding mirrorarranged in the optical path between the first optical imaging systemand the second optical imaging system; and a second optical path foldingmirror arranged in the optical path between the second optical imagingsystem and the third optical imaging system.

Then, the effective area (clear aperture) of the first optical pathfolding mirror and the effective area (clear aperture) of the secondoptical path folding mirror preferably have a reflective surface formedacross the whole of the planar surface. It is preferable that theeffective area of the first optical path folding mirror and the secondoptical path folding mirror not have a spatial overlap, and are arrangedsuch that the whole light beam from the first surface is guided to thesecond surface. With this structure, it is possible to effectivelycorrect chromatic aberration with only a radiation transmissive memberof a single type such as fluorite. Further, in the above-describedcatadioptric type projection optical system, all lenses comprising thefirst optical imaging system and the third optical imaging system arepreferably arranged along the single straight line of the optical axis.With this structure, assembly adjustment is comparatively easy and it ispossible to manufacture an optical system with excellent precision.

Next, according to yet another aspect of the present invention, theprojection optical system in the present invention includes a pluralityof lenses, a concave reflective mirror and a negative lens arranged inproximity to the concave reflective mirror, and is capable of forming areduced image of a first surface onto a second surface. Also, theprojection optical system moves the first surface and the second surfacein a scanning direction and, when used in an exposure apparatus to scanexpose the image of a first surface onto a second surface, it forms aslit-shaped or arc-shaped exposure area at the second surface when notscanning, and the numerical aperture of the second surface side is 0.82or more.

In this case, a concave reflective mirror and a negative lens arearranged along an optical axis in a direction substantially differentfrom the direction of gravity, and the following conditional expression(2) is preferably satisfied.1.0<S/|R|<1.8  (2)

In the conditional expression (2), S is the clear aperture (diameter) ofthe concave reflective mirror and R is the radius of curvature of theconcave reflective mirror.

By satisfying the conditional expression (2), it is possible tosubstantially suppress deformation due to the gravity of the concavereflective mirror and to ease manufacture. In other words, it is notpreferable that the value of the conditional expression (2) fall belowthe lower limit because the deformation of the concave reflective lensdue to gravity increases and assembly adjustment and working difficultyincreases. On the other hand, it is not preferable that the value of theconditional expression (2) rise above the upper limit because it becomesimpossible to correct chromatic aberration and field curvature whileassuring a large numerical aperture. It should be noted that to furtherdemonstrate the excellent effect of the present invention, the lowerlimit value of the conditional expression is preferably 1.1 and theupper limit value 1.65.

Next, exemplary embodiments of the present invention will be describedbased on the diagrams.

FIG. 5 shows a schematic view of the structure of an exposure apparatusprovided with the projection optical system of an exemplary embodimentof the present invention. It should be noted that in FIG. 5, the Z-axisis the wafer normal line direction, the Y-axis is parallel to the FIG. 5page surface and is perpendicular to the Z-axis, and the X-axis isperpendicular to the FIG. 5 page surface and perpendicular to theZ-axis. In the present exemplary embodiment, the present invention isapplied to a scanning projection exposure apparatus provided with acatadioptric projection optical system.

With reference to FIG. 5, the exposure apparatus in the presentembodiment provides an illumination apparatus 51 for illuminating areticle (mask) 50 arranged on a first surface. The illuminationapparatus 51 has a light source having an F₂ laser, for example, tosupply a light with a 157 nm wavelength, an optical integrator to form asecondary light source of a predetermined shape (circular, annular,bipolar, quadrupolar or the like) with the light from this light source,an illumination field stop for determining the illumination range on thereticle 50 and illuminates the illumination area on the reticle 50 witha nearly uniform illumination distribution.

Here, the illumination optical path in the illumination apparatus 51 ispreferably purged with an inert gas. The present embodiment purges withnitrogen. The reticle 50 is disposed on the reticle stage 53 and thereticle 50 and the reticle stage 53 are separated from the externalatmosphere by the casing 52. The inner space of this casing 52 ispreferably purged with an inert gas, and the present embodiment purgeswith nitrogen.

The light from the reticle 50 illuminated by the illumination apparatus51 is guided to the wafer 60 serving as a photosensitive substrate viathe projection optical system 400 having a plurality of lens elements(1-7, 9, 10, 13-18) formed with fluorite crystal, a concave reflectivemirror 11 and an aperture stop 20 or the like to control the coherencefactor (σ value), and the reticle 50 pattern image is formed in theexposure area at wafer 60. The projection optical path in the projectionoptical system 400 is preferably purged with an inert gas. The presentembodiment purges with helium.

The wafer 60 is disposed on the wafer stage 61 such that the wafersurface is positioned on the second surface serving as the image planeof the projection optical system 400, and the wafer 60 and the waferstage 61 are separated from the external atmosphere by the casing 62.The inner space of this casing 62 is preferably purged with an inertgas. The present embodiment purges with nitrogen. Also, the pattern onthe reticle 50 is transferred onto the exposure area of the wafer 60 byilluminating the reticle 50 while moving the reticle stage 53 and thewafer stage 61 along the Y-axis, which is the scanning direction,relative to the projection optical system 400 at a speed ratiocorresponding to the magnification of the projection optical system 400.

FIG. 6 shows the positional relationship between the optical axis andthe rectangular exposure area (that is, the effective exposure area)formed at a wafer. As shown in FIG. 6, in the present embodiment, in thecircular area (the image circle) IF having a radius B with the opticalaxis AX1 serving as the center, a rectangular effective exposure areaER, having a desired size in a position separated by an off-axis amountA in the—Y direction from the optical axis AX1, is determined. Here, LX(Ew) is the length in the X direction of the effective exposure area,and LY is the length in Y direction of the same.

In other words, in this embodiment, a rectangular effective exposurearea ER, having a desired size in a position separated by an off-axisamount A in the—Y direction from the optical axis AX1, is determined,and around the optical axis of the circular image circle IF the radius Bis predetermined such that the effective exposure area ER is containedwithin the circular image circle IF. Thus, in contrast, a rectangularillumination area (that is, the effective illumination area) having ashape and size corresponding to the effective exposure area in aposition separated by an off-axis amount A in the—Y direction from theoptical axis AX1 is formed at reticle 50.

With reference to FIG. 5 again, the projection optical system in thepresent embodiment is provided with a refractive first optical imagingsystem 100 to form a first intermediate image of the reticle 50 patternarranged on the first surface, a second optical imaging system 200comprised of a concave reflecting mirror 11 and two negative lenses 9,10 to form a second intermediate image (a secondary image of the reticlepattern at a magnification nearly equal to the first intermediate image)at a magnification nearly equal to the first intermediate image, andrefractive third optical imaging system 300 to form the final image ofthe reticle pattern (the reduced image of the reticle pattern) at thewafer 60 arranged on the second surface based on the light from thesecond intermediate image.

It should be noted that a first folding mirror 8 for deflecting thelight from the first optical imaging system 100 toward the secondoptical imaging system 200 is arranged in proximity to the formingposition of the first intermediate image in the optical path between thefirst optical imaging system 100 and the second optical imaging system200. Also, a second folding mirror 12 for deflecting the light from thesecond optical imaging system 200 toward the third optical imagingsystem 300 is arranged in proximity to the forming position of thesecond intermediate image in the optical path between the second opticalimaging system 200 and the third optical imaging system 300. The firstintermediate image and the second intermediate image are formed in theoptical path between the first optical path folding mirror 8 and thesecond optical imaging system 200, and in the optical path between thesecond optical imaging system 200 and the second optical path foldingmirror 12 respectively.

Further, both the first optical imaging system 100 and the third opticalimaging system 300 have a single optical axis extended in a straightline, that is, a standard optical axis AX1. The standard optical axisAX1 is positioned along the direction of gravity (that is, the verticaldirection). As a result, the reticle 50 and the wafer 60 are botharranged parallel along the surface orthogonal to the direction ofgravity, that is, the horizontal plane. In addition, all the lensescomprising the first optical imaging system 100 and all the lensescomprising the third optical imaging system 300 are arranged alonghorizontal planes at the standard optical axis AX1.

On the other hand, the second optical imaging system 200 also has anoptical axis AX2 extended in a straight line and this optical axis AX2is set such that it is orthogonal to the standard optical axis AX1.Furthermore, both the first optical path folding mirror 8 and the secondoptical path folding mirror 12 have a reflective surface on a planarsurface, and are integrally structured as one optical member (oneoptical path folding mirror FM) having two reflective surfaces. Thelines of intersection (strictly speaking, the intersecting lines of thevirtual extended planes) of these two reflective surfaces are set suchthat the optical axis AX1 of the first optical imaging system 100 andthe third optical imaging system 300, and the optical axis AX2 of thesecond optical imaging system 200 intersect at one point.

In the present embodiment, the concave reflective mirror 11 and thenegative lenses 9, 10 in the second optical imaging system compensatefor chromatic aberration and the positive Petzval sum generated by thefirst optical imaging system 100 and the third optical imaging system300 which are refractive optical systems including a plurality oflenses. Also, it is possible to form a second intermediate image inproximity to the first intermediate image when a second optical imagingsystem 200 has a structure with an imaging magnification of nearly unit(equal) magnification. In the present working embodiments, it ispossible to reduce the distance of the exposure area (that is, theeffective exposure area) from the optical axis, in other words, theoff-axis amount by an optical path separation in proximity to these twointermediate images. This is not only advantageous for aberrationcorrection, but also for size reduction, optical adjustment, machinedesign and manufacturing costs.

As described above, the second optical imaging system 200 alone holdsthe burden of compensating for the chromatic aberration and the Petzvalsum generated by the first optical imaging system 100 and the thirdoptical imaging system 300. This means it is preferable to set the powerof the concave reflection mirror 11 and the negative lenses 9, 10comprising the second optical imaging system 200 high. Thus, when thesymmetry of the second optical imaging system 200 deteriorates, thegeneration of asymmetrical chromatic aberration such as magnificationchromatic aberration and chromatic coma aberration becomes higher, and asufficient resolving power cannot be obtained. Therefore, in the presentembodiment, by adopting a structure capable setting the imagingmagnification of the second optical imaging system to nearly unitmagnification and capable of arranging a concave reflective mirror 11 inthe proximity of the pupil position, excellent asymmetry is obtained andgeneration of the above-described asymmetrical chromatic aberration issuccessfully prevented.

Hereinafter, the application of the present embodiment of the method inthe present invention to substantially avoid the effect of birefringencewill be described. First, with the lenses (16-18) arranged in theoptical path between wafer 60 and the aperture stop 20 arranged in thepupil position of the wafer side (the second surface side), there is atendency for the maximum angle of the transmitting light ray to theoptical axis to be large and it is easy to receive the effect ofbirefringence. Therefore, in the present embodiment, by applying methodsone through six of the present invention described above in combinationor alone, it is possible to obtain excellent optical characteristicswithout substantially receiving the effect of birefringence. It shouldbe noted that in FIG. 5 only three lenses can be arranged between theaperture stop 20 and the wafer 60 to simplify the diagram, but morelenses can be arranged in actual design.

Also, in a lens where the maximum angle of the transmitting light ray isgreater than 20 degrees to the optical axis, it is easy to receive theeffect of birefringence in spite of its arranged position. Therefore, inthe present embodiment, by applying methods one through six of thepresent invention described above in combination or alone in a lenswhere the maximum angle of the transmitting light ray is greater than 20degrees to the optical axis, it is possible to obtain excellent opticalcharacteristics without substantially receiving the effect ofbirefringence.

Furthermore, in a projection optical system in the present embodimentwith a large numerical aperture on the image side, the maximum angle tothe optical axis of the transmitting light ray in negative lenses 9, 10arranged in proximity to a concave reflective mirror 11 often becomeslarge for the purpose of aberration correction. Thus, in the presentembodiment, by applying methods one through six of the present inventionto these lenses 9, 10, it is possible to obtain excellent opticalcharacteristics without substantially receiving the effect ofbirefringence. It should be noted that when the number of negativelenses arranged in proximity to the concave reflective mirror 111 isgreater, methods one through six of the present invention may be appliedin combination or alone.

It should also be noted that, as described above, when applying thefirst method, the third method and the fifth method of the presentinvention, conditional expressions (3)-(5) are preferably satisfiedbetween the first lens group, the third lens group, the fifth lens groupand between the second lens group, the fourth lens group, the sixth lensgroup. Further, when applying the first method, the third method and thefifth method of the present invention, the first lens group (or thethird lens group; or the fifth lens group) and the second lens group (orthe fourth lens group; or the sixth lens group) are preferably formed asone optical member by optical contact or by adhesion. This structure isadvantageous because it limits the number of antireflective coats, as isused in an optical system using a F₂ laser in particular, because it ispossible to keep the number of optical surfaces on which anantireflective coat is to be formed to a minimum.

However, when applying the first method, the third method and the fifthmethod of the present invention, azimuth indicating is required betweenthe first lens group (or the third lens group; or the fifth lens group)and the second lens group (or the fourth lens group; or the sixth lensgroup). Thus, an aspherical surface that originally requires azimuthindicating, that is, the aspherical surface (an aspherical surface ofrotational asymmetric about the optical axis) for correcting aberrationat the time of lens adjustment is preferably used in the first lensgroup (or the third lens group; or the fifth lens group) or the secondlens group (or the fourth lens group; or the sixth lens group). In thiscase, even if a rotational asymmetrical scalar aberration occurs due tobirefringence, it is possible to correct it with an effect of theaspherical surface. Hereinafter, the aspherical surface for aberrationcorrection at the time of lens adjustment will be described. Whenmanufacturing a projection optical system, the position or posture of anoptical element such as a lens or a reflective mirror or the likecomprising a projection optical system is adjusted while measuringaberrations such as a wavefront aberration or the like and the opticalcharacteristics of a projection optical system are steered to a desiredvalue. However, only low order aberrations represented by Siedelaberrations can be corrected by adjusting the position or posture of anoptical element in such a manner. Therefore, for measured projectionoptical system aberrations, residual aberrations, except for thecomponent correctable by adjusting the position or posture of an opticalelement, is corrected by modifying the surface form of an opticalelement comprising a projection optical system, that is, using anaspherical surface. This kind of aspherical surface used for correctingresidual aberrations is called an aspherical surface for correctingaberrations at the time of lens adjustment, and a typical asphericalsurface form is a rotational asymmetric form relative to the opticalaxis. Therefore, in order to build an optical element provided with anaspherical surface for correcting aberrations at time of lens adjustmentinto an optical system, it is necessary to determine the azimuth anglearound the optical axis, that is, perform azimuth indicating.

Furthermore, even when the above-mentioned process by Burnett et al. andthe first-sixth processes of this invention are applied to a specifiedoptical member of a projection optical system, there are cases in whichpolarization aberration, that is, the phase difference between light ofa first polarization component going through the projection opticalsystem and light of a second polarization component, different from thefirst polarization component, cannot be completely corrected.

At this time, by arranging a film which decreases polarizationaberration, that is, a film having a characteristic of decreasing thephase difference between the first and second polarization components,on a surface of one or more of the optical members among the opticalmembers constituting the projection optical system, it is possible tofurther correct the polarization aberration.

Further, in the present embodiment, also effective is the method to forma crystal coat formed with fluorite crystal in the same manner as thesurface of the lens formed with fluorite crystal, and set it such thatthe crystal direction of the fluorite lens and the crystal direction ofthe crystal coat are substantially different. In this case, it is setsuch that the crystal direction along the optical axis of the fluoritelens and the crystal direction along the optical axis of the crystalcoat are substantially different. Alternatively, the crystal directionalong the optical axis of the fluorite lens and the crystal directionalong the optical axis of the crystal coat nearly align, and are setsuch that the fluorite lens and the crystal coat have a positionalrelationship relatively rotated only to a predetermined angle around theoptical axis. With this structure, it is possible to obtain excellentoptical characteristics without substantially receiving the effect ofbirefringence.

Hereinafter, working examples are described based on specific numbers.In each working example, fluorite (CaF₂) is used in all refractiveoptical members (lens components) comprising the projection opticalsystem. Also, the center oscillation wavelength of the F₂ laser lightbeing the exposure light is 157.6244 nm, and the refractive index ofCaF₂ in proximity to 157.6244 nm changes at a rate of −2.6*10⁻⁶ per+1 pmwavelength change, and changes at a rate of +2.6*10⁻⁶ per−1 pmwavelength change. In other words, in proximity to 157.6244 nm, thedistribution of the refractive index (dn/dλ) of CaF₂ is 2.6*10⁻⁶/pm.

Therefore, in each working example, the refractive index of CaF₂ for acenter wavelength of 157.6244 nm is 1.5593067, the refractive index ofCaF₂ for 157.6244 nm+1 pm=157.6254 nm is 1.5593041, and the refractiveindex of CaF₂ for 157.6244 nm−1 pm=157.6234 nm is 1.5593093.

Also, in each working example, an aspherical surface is described in thefollowing equation (a), where y is the height in the perpendiculardirection to the optical axis, z is the distance along the optical axisfrom the tangent plane at the vertex of the aspherical surface to theposition on the aspherical surface at height y (the sag amount), r isthe radius of curvature at vertex, κ is the constant of the cone, and Cnis the nth order of the aspherical coefficient.

Formula 1z=(y ² /r)/(1+(1−(1+κ)·y ² /r ²)^(1/2))+C ₄ ·y ⁴ +C ₆ +y ⁶ ·C ₈ ·y ⁸ +C₁₀ ·y ¹⁰ +C ₁₂ y ¹² +C ₁₄ y ¹⁴  (a)

In the working examples, the lens surfaces formed in an aspherical shapeare marked with an asterisk on the right side of the surface number.

First Working Example

FIG. 7 shows the lens structure of the projection optical system in thefirst working example. It should be noted that in the first workingexample, the present invention is applied to a projection optical systemwherein various aberrations including a chromatic aberration for anexposure light with a wavelength width of 157.6244 nm±1 pm have beencorrected.

In the projection optical system in FIG. 7, the first optical imagingsystem G1 (corresponding to 100 in FIG. 5) is comprised of, in orderfrom the reticle R (corresponding to 50 in FIG. 5), a biconvex lens L11,a negative meniscus lens L12 with the aspherical concave surface facingthe reticle side, a positive meniscus lens L13 with concave surfacefacing the reticle side, a positive meniscus lens L14 with theaspherical concave surface facing the wafer W (corresponding to 60 inFIG. 5) side, a negative meniscus lens L15 with the concave surfacefacing the reticle side, a positive meniscus lens L16 with the concavesurface facing the reticle side, a positive meniscus lens L17 with theconcave surface facing the reticle side, a biconvex lens L18, and apositive meniscus lens L19 with the aspherical concave surface facingthe wafer side.

Also, the second optical imaging system G2 (corresponding to 200 in FIG.5) is comprised of, in order from the reticle side (that is, theentrance side) along the light progression path to the second opticalsystem G2, a negative meniscus lens L21 with the aspherical concavesurface facing the reticle side, a negative meniscus lens L22 with theconcave surface facing the reticle side, and a concave reflective mirrorCM (corresponding to 11 in FIG. 5) with the concave surface facing thereticle.

Further, the third optical imaging system G3 (corresponding to 300 inFIG. 5) is comprised of, in order from the reticle side along the lightprogression direction, a positive meniscus lens L31 with the concavesurface facing the reticle, a biconvex lens L32, a positive meniscuslens L33 with the convex surface facing the reticle side, a biconcavelens L34 with the aspherical surface facing the reticle side, a positivemeniscus lens L35 with the aspherical concave surface facing the reticleside, a positive meniscus lens L36 with the aspherical concave surfacefacing the wafer side, an aperture stop AS, a biconvex lens L37, anegative meniscus lens L38 with the concave surface facing the reticleside, a planoconvex lens L39 with the flat surface facing the reticleside, a biconvex lens L310, a positive meniscus lens L311 with theaspherical concave surface facing the wafer side, a positive meniscuslens L312 with the convex surface facing the reticle side, and aplanoconvex lens L313 with the flat surface facing the wafer side.

The following table (1) shows the various values of the projectionoptical system in the first working example. In table (1), λ is thecenter wavelength of the exposure light, β is the projectionmagnification (the imaging magnification of the whole system), NA is thenumerical aperture of the image side (the wafer side), B is the radiusof the image circle IF on the wafer W, A is the off-axis amount of theeffective exposure area ER, LX (Ew) is the dimension (the long sidedimension) along the X direction of the effective exposure area ER, andLY is the dimension (the short side dimension) along the Y direction ofthe effective exposure area ER.

Also, the surface numbers represent the order of surfaces from thereticle side along the direction of the progression of the light rayfrom the reticle surface being the object surface (the first surface) tothe wafer surface being the image surface (the second surface); r is thecurvature radius of each surface (in the case of an aspherical surfacethe radius of curvature at vertex: mm); d is the axial spacing, that is,the surface spacing (mm); and n is the refractive index to the centerwavelength. It should be noted that the sign for surface spacing d ischanged for each reflection. Therefore, the sign for surface spacing dis negative in the optical path from the reflective surface of the firstoptical path folding mirror 8 to the concave reflective mirror CM and inthe optical path from the reflective surface of the second optical pathfolding mirror 12 to the image surface, the sign is positive in otheroptical paths.

Further, for first optical imaging system G1, the curvature radii ofconvex surfaces facing the reticle side are positive, and the curvatureradii of the concave surfaces are negative. On the other hand, for thethird optical imaging system G3, the curvature radii of concave surfacesfacing the reticle side are positive, and the curvature radii of theconvex surfaces are negative. Furthermore, for second optical imagingsystem G2, the curvature radii of concave surfaces facing the reticleside (that is, the entrance side) along the light progression path arepositive, and the curvature radii of the convex surfaces are negative.

The notations for table (1) described above are the same for table (2)below. TABLE 1 (Principal Dimensions) λ = 157.6244 nm β = −0.25 NA =0.84 B = 13.7 mm A = 3 mm LX (Ew) = 22 mm LY = 5 mm (Dimensions ofOptical Members) Surface Number r d n (reticle surface) 180.6367  1338.1128 43.1828 1.5593067 (lens L11)  2 −344.9356 1.0000  3* −599.998818.0000 1.5593067 (lens L12)  4 −750.0000 3.8448  5 −3025.0000 33.66101.5593067 (lens L13)  6 −248.3324 52.8928  7 123.3512 50.0000 1.5593067(lens L14)  8* 137.9069 94.2897  9 −79.1554 50.0000 1.5593067 (lens L15)10 −622.2967 11.3371 11 −184.1414 33.8374 1.5593067 (lens L16) 12−113.4803 14.3635 13 −449.4836 38.4631 1.5593067 (lens L17) 14 −145.44541.0000 15 990.3950 35.4539 1.5593067 (lens L18) 16 −266.8459 13.1001 17230.4657 43.1276 1.5593067 (lens L19) 18* 905.8792 86.0000 19 ∞−322.8159 (First Optical Path Folding Mirror 8) 20* 160.0000 −20.00001.5593067 (lens L21) 21 1029.3354 −39.7098 22 170.0000 −27.00001.5593067 (lens L22) 23 335.4155 −25.7429 24 211.5661 25.7429 (ConcaveReflective Mirror CM) 25 335.4155 27.0000 1.5593067 (lens L22) 26170.0000 39.7098 27 1029.3354 20.0000 1.5593067 (lens L21) 28* 160.0000322.8159 29 ∞ −109.1661 (Second Optical Path Folding Mirror 12) 30−2979.2971 −27.9776 1.5593067 (lens L31) 31 259.8472 −1.0000 32−274.0559 −32.1994 1.5593067 (lens L32) 33 788.0182 −1.0000 34 −226.6395−40.0000 1.5593067 (lens L33) 35 −775.7225 −17.4073 36* 286.8379−18.0000 1.5593067 (lens L34) 37 −220.3372 −218.2160 38* 800.0000−25.0000 1.5593067 (lens L35) 39 369.0625 −55.3479 40 −246.4360 −31.14781.5593067 (lens L36) 41* −707.1086 −33.8357 42 ∞ −5.0000 (Aperture StopAS) 43 −541.3470 −46.1825 1.5593067 (lens L37) 44 339.2085 −20.2043 45186.8545 −25.0000 1.5593067 (lens L38) 46 270.5486 −1.0000 47 ∞ −27.99031.5593067 (lens L39) 48 513.9686 −1.0000 49 −361.1692 −33.6260 1.5593067(lens L310) 50 3025.0000 −1.0000 51 −154.7547 −37.2001 1.5593067 (lensL311) 52* −576.9675 −1.0000 53 −139.4272 −33.3665 1.5593067 (lens L312)54 −736.4201 −3.6217 55 −1640.0282 −32.3202 1.5593067 (lens L313) 56 ∞−17.0000 (wafer surface) (aspherical surface data) Surface 3 κ =0.000000 C₄ = −6.00493 × 10⁻⁸ C₆ = 5.77252 × 10⁻¹³ C₈ = 1.82616 × 10⁻¹⁸C₁₀ = −4.73328 × 10⁻²² C₁₂ = 5.51714 × 10⁻²⁷ C₁₄ = 5.08985 × 10⁻³²Surface 8 κ = 0.000000 C₄ = −2.03240 × 10⁻⁷ C₆ = −2.35744 × 10⁻¹² C₈ =2.48815 × 10⁻¹⁵ C₁₀ = −3.92416 × 10⁻²⁰ C₁₂ = −3.37603 × 10⁻²³ C₁₄ =3.13488 × 10⁻²⁷ Surface 18 κ = 0.000000 C₄ = 1.02293 × 10⁻⁸ C₆ =−3.13320 × 10⁻¹⁴ C₈ = 7.13401 × 10⁻¹⁸ C₁₀ = −1.64420 × 10⁻²¹ C₁₂ =3.02692 × 10⁻²⁵ C₁₄ = −2.18460 × 10⁻²⁹ Surface 20 (Same surface assurface 28) κ = 0.000000 C₄ = −1.78974 × 10⁻⁸ C₆ = −3.14469 × 10⁻¹³ C₈ =−1.08289 × 10⁻¹⁷ C₁₀ = 1.61279 × 10⁻²² C₁₂ = −3.64258 × 10⁻²⁶ C₁₄ =2.91534 × 10⁻³⁰ Surface 36 κ = 0.000000 C₄ = −2.10087 × 10⁻⁸ C₆ =−4.27300 × 10⁻¹⁴ C₈ = 7.03324 × 10⁻¹⁸ C₁₀ = −8.90549 × 10⁻²³ C₁₂ =−5.62876 × 10⁻²⁶ C₁₄ = 3.85251 × 10⁻³⁰ Surface 38 κ = 0.000000 C₄ =2.53912 × 10⁻⁸ C₆ = 3.91063 × 10⁻¹³ C₈ = 7.05067 × 10⁻¹⁸ C₁₀ = 2.97494 ×10⁻²² C₁₂ = −1.09989 × 10⁻²⁶ C₁₄ = 3.64199 × 10⁻³¹ Surface 41 κ =0.000000 C₄ = −1.15678 × 10⁻⁸ C₆ = −1.04478 × 10⁻¹³ C₈ = −1.72165 ×10⁻¹⁸ C₁₀ = 3.51511 × 10⁻²² C₁₂ = −2.28722 × 10⁻²⁷ C₁₄ = 1.43968 × 10⁻³¹Surface 52 κ = 0.000000 C₄ = −3.26364 × 10⁻⁸ C₆ = −5.39112 × 10⁻¹³ C₈ =4.63415 × 10⁻¹⁷ C₁₀ = −6.39744 × 10⁻²¹ C₁₂ = 2.45549 × 10⁻²⁵ C₁₄ =−5.36486 × 10⁻³⁰ (Values For Conditional Expressions) Dw = 17 mm Nw =0.84 Ew = 22 mm S = 283.0471 mm R = 211.5661 mm (1) (Dw · Nw)/Ew = 0.649(2) S/|R| = 1.338

FIG. 8 shows the lateral aberrations in the first working example. Inthe aberration diagram, Y is the image height, the solid line is thecenter wavelength 157.6244 nm, the dotted line is the wavelength157.6244 nm+1 pm=157.6254 nm, the dot-dashed line is the wavelength157.6244 nm−1 pm=157.6234 nm. As is clear from the aberration diagram,the chromatic aberration in the first working example is effectivelycorrected for an exposure light with a wavelength bandwidth of 157.624nm+1 pm.

Second Working Example

FIG. 9 shows the lens structure of the projection optical systemdescribed in the second working example. It should be noted that thesecond working example adopts the present invention the same as thefirst embodiment in a projection optical system with various aberrationsincluding chromatic aberrations corrected for an exposure light with awavelength bandwidth of 157.6244 nm±1 pm.

In the projection optical system in FIG. 9, beginning from the reticleside, the first optical imaging system G1 is comprised of a biconvexlens L11, a negative meniscus lens L12 with the aspherical concavesurface facing the reticle side, a positive meniscus lens L13 with theconcave lens facing the reticle side, a positive meniscus lens L14 withthe concave surface facing the reticle, a biconcave lens L15, a positivemeniscus lens L16 with the concave lens facing the reticle side, apositive meniscus L17 with the concave lens facing the reticle side, abiconvex lens L18, and a positive meniscus lens L19 with the asphericalconcave surface facing the wafer side.

Also, beginning in order from the reticle side (in other words, theentrance side) along the light progression direction, the second opticalimaging system G2 is comprised of a negative meniscus lens L21 with theaspherical concave side facing the reticle side, a negative meniscus L22with the aspherical concave side facing the reticle, and a concavereflective mirror CM with the concave surface facing the reticle.

Furthermore, beginning in order from the reticle side along the lightprogression direction, the third optical imaging system G3 is comprisedof a positive meniscus lens L31 with the concave surface facing thereticle side, a biconvex lens L32, a positive meniscus lens L33 with theconvex surface facing the reticle side, a biconcave lens L34 with theaspherical concave surface facing the reticle side, a positive meniscuslens L35 with the aspherical concave surface facing the reticle side, apositive meniscus lens L36 with the aspherical concave surface facingthe wafer side, an aperture stop AS, a biconvex lens L37, a negativemeniscus lens L38 with the concave surface facing the reticle side, aplanoconvex lens L39 with the plane surface facing the reticle side, abiconvex lens L310, a positive meniscus lens L311 with the asphericalconcave side facing the wafer side, a positive meniscus lens L312 withthe convex side facing the reticle side, and a planoconvex lens L313with the plane side facing the wafer side.

The various dimensions of the projection optical system in the secondworking example are listed in the next table (2). TABLE 2 (PrincipleDimensions) λ = 157.6244 nm β = −0.25 NA = 0.84 B = 13.7 mm A = 3 mm LX(Ew) = 22 mm LY = 5 mm (Dimensions of Optical Members) Surface Number rd n (reticle surface) 134.0611  1 262.9619 50.0000 1.5593067 (lens L11) 2 −690.2912 114.9165  3* −599.9988 18.0000 1.5593067 (lens L12)  4−750.0000 1.0000  5 −3025.0000 27.9713 1.5593067 (lens L13)  6 −244.858943.6281  7 114.5751 28.3042 1.5593067 (lens L14)  8* 175.8195 92.1920  9−109.5355 45.7658 1.5593067 (lens L15) 10 997.5337 10.1935 11 −331.547144.1807 1.5593067 (lens L16) 12 −131.7230 43.6830 13 −1519.9100 38.68641.5593067 (lens L17) 14 −166.0874 44.0031 15 508.0358 27.8372 1.5593067(lens L18) 16 −487.9084 8.7669 17 265.5991 22.9898 1.5593067 (lens L19)18* 1561.9630 86.0000 19 ∞ −264.6314 (First Optical Path Folding Mirror8) 20 127.3620 −20.0000 1.5593067 (lens L21) 21 702.6119 −31.1397 22*164.9999 −27.0000 1.5593067 (lens L22) 23 422.8572 −43.0899 24 196.526143.0899 (Concave Reflective Mirror CM) 25 422.8572 27.0000 1.5593067(lens L22) 26* 164.9999 31.1397 27 702.6119 20.0000 1.5593067 (lens L21)28 127.3620 264.6314 29 ∞ −85.0000 (Second Optical Path Folding Mirror12) 30 2164.9673 −24.7566 1.5593067 (lens L31) 31 219.1763 −1.0000 32−296.9471 −26.3606 1.5593067 (lens L32) 33 1129.3092 −20.0736 34−243.2548 −28.2049 1.5593067 (lens L33) 35 −1226.1325 −37.0789 36*249.2995 −18.0000 1.5593067 (lens L34) 37 −367.2759 −192.0672 38*800.0000 −28.4116 1.5593067 (lens L35) 39 247.6103 −30.2659 40 −246.9554−33.9672 1.5593067 (lens L36) 41* −1000.0000 −20.9789 42 ∞ −5.0000(Aperture Stop AS) 43 −420.5483 −47.2146 1.5593067 (lens L37) 44412.3925 −21.7678 45 197.9152 −25.0000 1.5593067 (lens L38) 46 280.6330−1.0000 47 ∞ −27.1468 1.5593067 (lens L39) 48 531.5277 −1.0000 49−422.7241 −30.3630 1.5593067 (lens L310) 50 3025.0000 −1.0000 51−191.0370 −31.1678 1.5593067 (lens L311) 52* −674.8686 −1.0000 53−128.0047 −34.6343 1.5593067 (lens L312) 54 −583.8584 −7.3608 55−681.9357 −18.000 1.5593067 (lens L313) 56 ∞ −20.0000 (wafer surface)(aspherical surface data) Surface 3 κ = 0.000000 C₄ = −8.56936 × 10⁻⁸ C₆= 2.46201 × 10⁻¹² C₈ = −1.55668 × 10⁻¹⁶ C₁₀ = 9.43386 × 10⁻²¹ C₁₂ =−6.07941 × 10⁻²⁵ C₁₄ = 2.17159 × 10⁻²⁹ Surface 8 κ = 0.000000 C₄ =−1.69055 × 10⁻⁷ C₆ = 2.05649 × 10⁻¹² C₈ = 2.63740 × 10⁻¹⁵ C₁₀ = −1.76419× 10⁻¹⁹ C₁₂ = −5.01834 × 10⁻²⁴ C₁₄ = 9.35851 × 10⁻²⁸ Surface 18 κ =0.000000 C₄ = 1.24311 × 10⁻⁸ C₆ = −6.42840 × 10⁻¹⁴ C₈ = 3.52871 × 10⁻¹⁸C₁₀ = −1.74809 × 10⁻²² C₁₂ = 3.51815 × 10⁻²⁶ C₁₄ = −3.53925 × 10⁻³⁰Surface 22 (Same surface as surface 26) κ = 0.000000 C₄ = −2.43802 ×10⁻⁸ C₆ = −8.60903 × 10⁻¹³ C₈ = −1.80247 × 10⁻¹⁷ C₁₀ = −2.47315 × 10⁻²²C₁₂ = −6.90946 × 10⁻²⁹ C₁₄ = −1.56721 × 10⁻³¹ Surface 36 κ = 0.000000 C₄= −5.26088 × 10⁻⁹ C₆ = 8.00291 × 10⁻¹³ C₈ = −2.02514 × 10⁻¹⁶ C₁₀ =1.45524 × 10⁻²⁰ C₁₂ = −5.76378 × 10⁻²⁵ C₁₄ = −1.52735 × 10⁻³¹ Surface 38κ = 0.000000 C₄ = 3.20217 × 10⁻⁸ C₆ = 4.27793 × 10⁻¹³ C₈ = −1.75553 ×10⁻¹⁷ C₁₀ = 8.55718 × 10⁻²² C₁₂ = −2.67846 × 10⁻²⁶ C₁₄ = 4.75297 × 10⁻³¹Surface 41 κ = 0.000000 C₄ = −1.46322 × 10⁻⁸ C₆ = 6.43322 × 10⁻¹⁴ C₈ =−2.51761 × 10⁻¹⁷ C₁₀ = 1.37244 × 10⁻²¹ C₁₂ = −2.75604 × 10⁻²⁶ C₁₄ =3.93456 × 10⁻³¹ Surface 52 κ = 0.000000 C₄ = −3.13761 × 10⁻⁸ C₆ =−8.78276 × 10⁻¹³ C₈ = 9.23919 × 10⁻¹⁷ C₁₀ = −1.30689 × 10⁻²⁰ C₁₂ =7.70494 × 10⁻²⁵ C₁₄ = −2.28846 × 10⁻²⁹ (Values For ConditionalExpressions) Dw = 20 mm Nw = 0.84 Ew = 22 mm S = 286.7831 mm R =196.5261 mm (1) (Dw · Nw)/Ew = 0.764 (2) S/|R| = 1.459

FIG. 10 shows the lateral aberrations in the second working example. Inthe aberration diagram, Y is the image height, the solid line is thecenter wavelength 157.6244 nm, the dotted line is the wavelength157.6244 nm+1 pm=157.6254 nm, the dot-dashed line is the wavelength157.6244 nm−1 pm=157.6234 nm. As is clear from the aberration diagram,the chromatic aberration in the second working example is effectivelycorrected similar to the first working example for an exposure lightwith a wavelength bandwidth of 157.624 nm±1 pm.

As described above in each working example, it is possible toeffectively avoid contamination of the lenses caused by outgas from thephotoresist coated on the wafer W because the conditional expression (1)is satisfied. Also, in each working example the concave reflectivemirror CM and the negative lenses (L21, L22) are arranged along thelight axis AX2 in the direction orthogonal to the direction of gravity,but because conditional expression (2) is satisfied, distortions of theconcave reflective mirror CM caused by gravity are kept low, andassembly adjustment and working are eased.

In a projection optical system according to a third embodiment, apolarization aberration (i.e., a phase difference between light of afirst polarization component having a vibration (polarization) directionin a predetermined direction and light of a second polarizationcomponent having a vibration (polarization) direction different from thefirst polarization direction) which is generated by intrinsicbirefringence of an isometric (cubic) crystal optical material (e.g.,fluorite) constituting the projection optical system is corrected by athin film arranged on the surface of the optical material.

In the third embodiment, in order to make an incident state of lightincident to the thin film the same as in a real case, a projectionoptical system shown in FIG. 13 is considered. FIG. 13 is a diagramshowing a lens structure of a projection optical system according to thethird embodiment. The projection optical system of FIG. 13 is differentfrom the above-mentioned first and second embodiments, and applies thisinvention to a dioptric type projection optical system in which aplurality of refractive optical members are arranged along a linearoptical axis.

From the reticle R side, in order, the projection optical system of FIG.13 is constituted by a negative meniscus lens L1 having a concavesurface facing the wafer W side, a negative meniscus lens L2 having aconcave surface facing the reticle R side, two positive meniscus lensesL3, L4 having a concave surface facing the reticle R side, threepositive meniscus lenses L5-L7 having a convex surface facing thereticle R side, a negative meniscus lens L8 having a concave surfacefacing the wafer W side, three biconcave lenses L9-L11, a biconvex lensL12, a positive meniscus lens L13 having a concave surface facing thereticle R side, a biconvex lens L14, an aperture stop AS, a biconvexlens L15, a negative meniscus lens L16 having a concave surface facingthe reticle R side, a positive meniscus lens L17 having a concavesurface facing the reticle R side, three positive meniscus lensesL18-L20 having a concave surface facing the wafer W side, a planoconcavelens L21 having a concave surface facing the reticle R side, and aparallel flat plate L22.

FIG. 14 is a diagram showing a positional relationship between anoptical axis and a rectangular-shaped exposure region (i.e., effectiveexposure region) formed on the wafer W by a projection optical systemaccording to the third embodiment. As shown in FIG. 14, in the thirdembodiment, within a round-shaped region (image circle) IF having aradius B about an optical axis AX1, a rectangular-shaped effectiveexposure region ER having a desired size is set at a position includingthe optical axis AX1. Here, the length of the effective exposure regionER in the X direction is LX, and the length in the Y direction is LY.Furthermore, an off-axis amount A of the effective exposure region ER inthe projection optical system of the third embodiment is 0.

The respective values of the projection optical system according to thethird embodiment are shown in the following Table (3). In Table (3), λis the wavelength of exposure light, β is the projection magnification,NA is the image side (wafer side) numerical aperture, B is the radius ofan image circle IF on the wafer W, LX is a dimension along the Xdirection (dimension of the long side) of the effective exposure regionER, and LY is a dimension along the Y direction (dimension of the shortside) of the effective exposure region ER, respectively.

Furthermore, the surface number refers to the order of the surface fromthe reticle side along the direction in which a light beam advances fromthe reticle plane, which is an object plane (first plane), to a wafersurface, which is an image plane (second plane); r is the radius ofcurvature (the radius of curvature at the vertex in the case of anaspherical surface: mm) of each surface; d is an on-axis distance ofeach surface, that is, the distance between surfaces (mm); material isthe name of the material of the light transmissive member; and coatingis the type of an optical thin film arranged on the surface of the lighttransmissive member. Additionally, in the “radius of curvature” columnof each surface, a radius of curvature of a convex surface facing thereticle side is positive, and a radius of curvature of a concave surfaceis negative. Furthermore, in the “coating” column, ID indicates an idealoptical thin film (that is, a thin film in which transmittance is 100%and no phase difference is given to light passing therethrough), and REindicates a thin film having a phase difference decreasing functionwhich will be described later.

In the third embodiment, the refractive index n of fluorite with respectto a wavelength λ of exposure light is n=1.55930666. TABLE 3 (PrincipalValues) λ = 157.62 nm β = −0.25 NA = 0.85 B = 11.3 mm A = 0 LX = 22 mmLY = 5 mm (Optical Member Values) Surface Number r d Material CoatingObject 0.0000 55.0000 Plane  1 1760.1477 13.0000 fluorite ID  2*154.1222 31.5550 ID  3 −100.0051 35.1768 fluorite ID  4 −204.4440 0.2632ID  5* −229.9998 49.8862 fluorite ID  6 −205.2327 1.0000 ID  7−1022.4100 43.9568 fluorite ID  8 −240.0184 1.0000 ID  9 305.305543.3393 fluorite ID 10 13811.5160 1.0000 ID 11 260.0366 49.9927 fluoriteID 12 1061.5609 1.6965 ID 13 201.2791 44.9989 fluorite ID 14* 1264.28641.0008 ID 15 746.2630 41.9997 fluorite ID 16 554.5437 9.6189 ID 17−1904.6110 41.9988 fluorite ID 18 100.8840 66.1124 ID 19* −133.647113.1297 fluorite ID 20 347.1443 81.4331 ID 21 −191.2608 47.9972 fluoriteID 22* 1567.7421 6.8417 ID 23 2383.7446 45.8049 fluorite ID 24 −254.28861.0005 ID 25* −826.9931 27.1939 fluorite ID 26 −318.6391 1.0003 ID 27812.6131 58.9358 fluorite ID 28 −339.1799 3.0000 ID 29 0.0000 35.7374 ID30 1993.9339 60.0000 fluorite ID 31 −299.7702 14.3166 ID 32 −250.356731.9046 fluorite ID 33 −409.2235 1.0000 ID 34 −3543.3950 36.4233fluorite ID 35 −493.5664 1.0000 ID 36 326.4763 35.6384 fluorite ID 372606.2523 1.0000 ID 38 150.1197 55.0000 fluorite ID 39* 339.1014 6.3990ID 40 213.3769 27.0460 fluorite ID 41 744.7389 4.2700 ID 42 −17499.230026.5000 fluorite (C1) RE 43 0.0000 1.5001 RE 44 0.0000 26.5000 fluorite(C2) RE 45 0.0000 8.0001 RE (Aspherical Surface Data) 2^(nd) Surface κ =0.000000 C₄ = −2.27515 × 10⁻⁷ C₆ = 9.94921 × 10⁻¹² C₈ = −4.92700 × 10⁻¹⁶C₁₀ = 5.54636 × 10⁻²⁰ C₁₂ = 2.11035 × 10⁻²⁴ C₁₄ = 3.99019 × 10⁻²⁸ 5^(th)Surface κ = 0.000000 C₄ = −8.03956 × 10⁻¹⁰ C₆ = 3.19003 × 10⁻¹³ C₈ =2.22399 × 10⁻¹⁷ C₁₀ = 5.84971 × 10⁻²¹ C₁₂ = −3.73576 × 10⁻²⁵ C₁₄ =7.97949 × 10⁻²⁹ 14^(th) Surface κ = 0.000000 C₄ = 2.25598 × 10⁻⁸ C₆ =−2.34895 × 10⁻¹³ C₈ = 6.24176 × 10⁻¹⁸ C₁₀ = 3.33460 × 10⁻²² C₁₂ =−1.10294 × 10⁻²⁶ C₁₄ = 9.31768 × 10⁻³¹ 19^(th) Surface κ = 0.000000 C₄ =2.76204 × 10⁻⁸ C₆ = 3.44284 × 10⁻¹² C₈ = 2.88450 × 10⁻¹⁶ C₁₀ = 2.69641 ×10⁻²⁰ C₁₂ = 2.97751 × 10⁻²⁴ C₁₄ = 1.90637 × 10⁻²⁸ 22^(nd) Surface κ =0.000000 C₄ = 4.32103 × 10⁻⁸ C₆ = −5.61223 × 10⁻¹³ C₈ = −2.19658 × 10⁻¹⁷C₁₀ = 9.46389 × 10⁻²² C₁₂ = 8.20013 × 10⁻²⁷ C₁₄ = −8.47779 × 10⁻³¹25^(th) Surface κ = 0.000000 C₄ = −1.71489 × 10⁻⁸ C₆ = 5.86948 × 10⁻¹⁴C₈ = −2.42163 × 10⁻¹⁸ C₁₀ = 8.02913 × 10⁻²³ C₁₂ = −4.45790 × 10⁻²⁷ C₁₄ =2.64310 × 10⁻³¹ 39^(th) Surface κ = 0.000000 C₄ = −4.30405 × 10⁻⁸ C₆ =2.47690 × 10⁻¹² C₈ = −3.60186 × 10⁻¹⁷ C₁₀ = −5.22555 × 10⁻²¹ C₁₂ =4.93476 × 10⁻²⁵ C₁₄ = −1.51028 × 10⁻²⁹

In the third embodiment, with respect to the two light transmittingmembers closest to the wafer W side (lenses L21, L22) whose incidentangle ranges are large with respect to the light transmitting members, apolarization aberration correction effect by a thin film was considered.In the third embodiment, among the plurality of optical members L1-L22,it is assumed that only the two optical members L21, L22 which arelocated closest to the wafer W side have intrinsic birefringence. Withintrinsic birefringence of the fluorite that forms these opticalmembers, the difference between the value of double refraction in thewavelength of exposure light in the direction of a crystal axis [110]and the value of double refraction in the wavelength of exposure lightin the direction of a crystal axis [100] is −3.3 nm/cm. Furthermore, theoptical members, L21, L22 are formed so that the crystal axis [111]matches the optical axis AX1, and all the crystal axes different fromthe crystal axis [111] of the optical members L21, L22 have a positionalrelationship which is relatively rotated 60° about the optical axis AX1.That is, the fifth process of this invention is applied to the opticalmembers L21, L22.

Next, a comparison is shown between the case of arranging an idealoptical thin film ID on a surface (lens surface) of the optical membersL21, L22, and the case of arranging a thin film RE having a phasedifference decreasing function. Here, an ideal optical thin film is atheoretical thin film in which transmittance of the thin film RE is100%, and which has an effect of imparting no phase difference to lightof a plurality of polarization components passing through the thin film.Furthermore, the thin film RE having a phase difference decreasingfunction has a structure shown in the following table (4).

In the following table (4), λ shows a center wavelength of exposurelight. Furthermore, the layer number shows the order of the layer fromthe side of the base material on which the thin film is arranged, Dshows the thickness (nm) of each layer, and n shows the refractive indexwith respect to a center wavelength of each layer. TABLE 4 λ = 157.62 nmLayer Number D n 11^(th) layer 37.19 1.418 10^(th) layer 21.41 1.78 9^(th) layer 24.88 1.418  8^(th) layer 15.37 1.78  7^(th) layer 20.351.418  6^(th) layer 16.64 1.78  5^(th) layer 24.74 1.418  4^(th) layer17.76 1.78  3^(rd) layer 20.6 1.418  2^(nd) layer 10.68 1.78  1^(st)layer 13.85 1.418 Substrate

FIG. 15 shows an incident angle characteristic of transmittance of thethin film RE of Table (4), and FIG. 16 shows an incident anglecharacteristic of a phase difference of the thin film RE of Table (4).Furthermore, in FIG. 15, transmittance is shown on the vertical axis,and the incident angle (0 in the case of vertical incidence) withrespect to the thin film RE is shown on the horizontal axis.Additionally, the broken line of FIG. 15 shows incident angle dependenceof transmittance of the thin film RE with respect to a P polarizationcomponent (polarization component in which an oscillation directionwhich is within the incident surface, that is, a polarization componenthaving a polarization plane along a diameter direction of a circle aboutan axis parallel to the optical axis). The solid line shows incidentangle dependence of transmittance of the thin film RE with respect to anS polarization component (a polarization component which is within aplane in which an oscillation direction is perpendicular to an incidentsurface, that is, a polarization component having a polarization planealong a circumferential direction of a circle about an axis parallel tothe optical axis).

Furthermore, in FIG. 16, a phase difference (°) of the P polarizationcomponent and the S polarization component after passing through thethin film RE is shown on the vertical axis, and the incident angle (0 inthe case of vertical incidence) is shown on the horizontal axis.

As is clear from FIG. 15, the thin film RE ensures transmittance of 98%or more in an incident angle range corresponding to NA=0.85 (that is, anincident angle range up to sin⁻¹ (0.85)) and shows a standard whichholds up sufficiently to use in practice. Furthermore, as is clear fromFIG. 16, the phase difference between the P polarization component andthe S polarization component at an incident angle corresponding toNA=0.85 is less than 8°, with the phase of the P polarization componentbeing more advanced than the phase of the S polarization component. Thatis, with respect to the light transmitting through the thin film RE, asthe incident angle becomes large, the phase of the light of the Ppolarization component advances more than the phase of the light of theS polarization component.

As described in the third embodiment, when both L21, L22 of the opticaltransmitting members have an optical axis AX1 matching the crystal axis[111], have substantially the same thickness, and have a positionalrelationship in which the crystal axes different from the crystal axis[111] are relatively rotated 60° about the optical axis AX1, a pair L21,L22 of the optical members have a fast axis such that the phase of thelight of the S polarization component advances more than the phase ofthe light of the P polarization component as the incident angle becomeslarger. Here, the above-mentioned thin film RE has a fast axisperpendicular to a pair L21, L22 of the optical members, so the totalphase difference can be decreased by this thin film RE.

FIG. 17 is a graph showing a comparison between a wavefront aberrationwhen a thin film RE is arranged on a pair L21, L22 of the opticalmembers located closest to the wafer W side and a wavefront aberrationwhen an ideal optical thin film ID is arranged instead of the thin filmRE, in a projection optical system having various values shown in table(3). Furthermore, in FIG. 17, X shows a wavefront aberration (mλRMS) ofa polarization component having an oscillation direction (polarizationplane) in the X direction of FIG. 14, and Y shows a wavefront aberration(mλRMS) of a polarization component having an oscillation direction(polarization plane) in the Y direction of FIG. 14.

With reference to FIG. 17, it is clear that the phase differencecorrection ability of the thin film RE is sufficiently high.Furthermore, it is also clear that an optical performance capability(imaging performance capability) of a projection optical system can beextremely improved.

It should be noted that fluorite serves as the birefringent opticalmaterial in the above-described embodiments; however the invention isnot limited to this. Other single axis crystals such as barium fluoride(BaF₂), lithium fluoride (LiF), sodium fluoride (NaF), strontiumfluoride (SrF₂), or the like may be used. In this case, the crystal axisdirection of barium fluoride (BaF₂) or the like is preferably determinedaccording to the present invention.

In the exposure apparatus in the above-described embodiments, it ispossible to fabricate microdevices (semiconductor elements, image pickupdevices, liquid crystal display devices, thin film magnetic heads, orthe like) by illuminating (an illumination step) a mask (a reticle) viaan illumination optical system, and exposing (an exposure step) apattern for transfer formed on the mask onto a photosensitive substrateusing a projection optical system. With reference to the flowchart inFIG. 11, an example of a method, when obtaining a semiconductor deviceserving as a microdevice, for forming a predetermined circuit pattern ona wafer or the like serving as a photosensitive substrate using theexposure device in the present embodiments will be described.

First, in step 301 of FIG. 11, a metal film is vapor deposited on onelot of wafers. Next, in step 302, a photoresist is applied to the metalfilm on the lot of wafers. After that, in step 303, using the exposureapparatus in the present embodiments, the image of a pattern on a maskis successively exposure transferred to each shot region on the lot ofwafers via the projection optical system. After that, in step 304, afterthe photoresist on the lot of wafers is developed, the circuit patterncorresponding to the pattern on the mask is formed on each shot regionon each wafer by etching, in step 305, the resist pattern serving as amask on the lot of wafers.

After that, a semiconductor element or the like is fabricated byperforming circuit pattern formation or the like on successive layers.According to the above-described semiconductor device fabricationmethod, it is possible to obtain, with good throughput, a semiconductordevice having a very detailed circuit pattern. It should be noted that,in steps 301 through 305, metal is vapor deposited on the wafer, aresist is coated on the metal thin film, and then the exposure,developing, and etching processes are performed, but before theseprocesses are performed, it is also possible to, after forming a siliconoxide film on the wafer, to coat a resist on the silicon oxide film andthen perform the exposure, developing, and etching processes.

In the exposure apparatus in the preferred embodiments, it is possibleto obtain a liquid crystal display element serving as a microdevice byforming a predetermined pattern (a circuit pattern, an electrodepattern, or the like) on a plate (a glass substrate). Below, withreference to the flowchart in FIG. 12, the method in this process willbe described. In FIG. 12, the so-called photolithography step, whichtransfer exposes a mask pattern to a photosensitive substrate (a glasssubstrate with a resist applied, or the like) using the exposureapparatus in the embodiments, is performed in the pattern formation step401. A predetermined pattern containing a plurality of electrodes or thelike is formed on the photosensitive substrate in the photolithographystep. After that, by passing the exposed pattern through each of thedevelopment step, the etching step, the mask removal step or the like,the predetermined pattern is formed on the substrate, and the processmoves to the color filter formation step 402.

Next, in the color filter formation step 402, a plurality of sets ofthree dots corresponding to R (Red), G (Green), and B (Blue) arearranged in a matrix form, or sets of three stripe filters of R, G, Barranged in the direction of a plurality of horizontal scan lines toform a color filter. After the color filter formation step 402, the cellassembly step 403 is executed. In the cell assembly step, a liquidcrystal panel (a liquid crystal cell) is assembled using the substratehaving a predetermined pattern obtained in the pattern formation step401, and the color filter obtained in the color filter formation step402. In the cell assembly step 403, liquid crystal material is injectedbetween the substrate having a predetermined pattern obtained in thepattern formation step 401 and the color filter obtained in the colorfilter formation step 402, for example, thereby fabricating a liquidcrystal panel (a liquid crystal cell).

After that, in the module assembly step 404, each part, an electriccircuit for operating the assembled liquid crystal display (the liquidcrystal cell), a backlight or the like are attached, completing a liquidcrystal display element. According to the above-described liquid crystaldisplay element fabrication method, it is possible to obtain a liquidcrystal display element having a very detailed pattern, with goodthroughput.

It should be noted that in the above-described embodiments, the presentinvention has been applied to the projection optical system installed inan exposure apparatus; but the invention is not being limited to this.It is also possible to apply the present invention to other projectionoptical systems. Also, in each of the above-described embodiments an F2laser light source is used to supply a 157 nm wavelength light; but theinvention is not limited to this. It is possible to use, for example, anArF excimer laser light source to supply a 193 nm wavelength light, anAr2 laser light source to supply a 126 nm wavelength light, or a Kr₂laser light source to supply a 146 nm wavelength light.

As described above, it is possible with the present invention to realizea projection optical system having excellent optical performance withoutsubstantially being affected by birefringence in spite of using opticalmaterial with intrinsic birefringence such as fluorite, for example.Also, it is possible to realize a projection optical system capable ofeffectively avoiding contamination of the lenses caused by outgas fromthe photoresist. Therefore, by providing the projection optical systemin the present invention in an exposure apparatus, it is possible tofabricate excellent microdevices, through high precision projectionexposure using a high resolution projection optical system.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments or constructions. To the contrary,the invention is intended to cover various modifications and equivalentarrangements conceived by those skilled in lithographic systems. Inaddition, while the various elements of the preferred embodiments areshown in various combinations and configurations, which are exemplary,other combinations and configurations, including more, less or only asingle element, are also within the spirit and scope of the invention.

1. A projection optical system capable of forming a reduced image of afirst surface at a second surface, and that includes a plurality oflenses and at least one concave reflective mirror, wherein theprojection optical system: when used in an exposure apparatus to scanexpose the first surface at the second surface while moving the firstsurface and the second surface along a scanning direction, forms aslit-shaped or arc-shaped exposure area at the second surface when notscanning; and satisfies the condition0.5<(Dw·Nw)/Ew<1.4  (1) where Dw is a working distance of the secondsurface side, Nw is a numerical aperture of the second surface side, andEw is a length in a direction orthogonal to the scanning direction ofthe slit-shaped or arc-shaped exposure area.
 2. A projection opticalsystem according to claim 1, wherein the slit-shaped or arc-shapedexposure area does not intersect an optical axis of the projectionoptical system, and the projection optical system further comprises: a)a refractive type first optical imaging system to form a firstintermediate image of the first surface; b) a second optical imagingsystem, having at least one negative lens and a concave reflectivemirror, to form the first intermediate image into a second intermediateimage of nearly the same magnification near the first intermediate imageforming position based on the light beam from the first intermediateimage; c) a refractive type third optical imaging system to form areduced image of the second intermediate image onto the second surfacebased on the light beam from the second intermediate image; d) a firstoptical path folding mirror arranged in the optical path between thefirst optical imaging system and the second optical imaging system; ande) a second optical path folding mirror arranged in the optical pathbetween the second optical imaging system and the third optical imagingsystem.
 3. A projection optical system according to claim 2, wherein alllenses comprising the first optical imaging system and the third opticalimaging system are arranged along a single straight line along theoptical axis.
 4. An exposure apparatus comprising: an illuminationsystem to illuminate a mask serving as the first surface; and aprojection optical system according to claim 1 to form an image of apattern on the mask onto a photosensitive substrate serving as thesecond surface.
 5. A projection optical system including a plurality oflenses, a concave reflective mirror and a negative lens arranged inproximity to the concave reflective mirror, and capable of forming areduced image of a first surface at a second surface, wherein theprojection optical system: a) when used in an exposure apparatus to scanexpose the first surface at the second surface while moving the firstsurface and the second surface along a scanning direction, forms aslit-shaped or arc-shaped exposure area at the second surface when notscanning; and b) a numerical aperture of the second surface side is 0.82or more.
 6. A projection optical system according to claim 5, wherein:a) the concave reflective mirror and the negative lens are arrangedalong an optical axis in a direction substantially different from adirection of gravity, and b) the following conditional expression issatisfied:1.0<S/|R|<1.8  (2) wherein S is a clear aperture (diameter) of theconcave reflective mirror and R is a radius of curvature of the concavereflective mirror.
 7. An exposure apparatus comprising: an illuminationsystem to illuminate a mask serving as the first surface; and aprojection optical system according to claim 5 to form an image of apattern on the mask onto a photosensitive substrate serving as thesecond surface.